[major] Make the shared vocabulary drive C# emission, not just check it

CLAUDE.md

@@ -105,10 +105,18 @@ does not compile — which makes every claim in `integrals` and `derivatives` ch
 contradict is refused by name, with both dimensions written out, rather than emitted as something
 broken. Four are refused as the metadata stands.
 
-The check itself now lives in `Semantics.Vocabulary` and both generators run it. C++ refuses the
-four; C# reports them as SEM008 and emits the operators anyway, because removing an operator from a
-shipped package is a breaking change. So the table below is what C++ does not write **and** what C#
-writes with a warning against its name:
+The check itself lives in `Semantics.Vocabulary`, and the vocabulary is what both generators emit
+*from* rather than merely check against — `QuantityVocabulary.Types` is the list of classes to write
+and `QuantityVocabulary.Relationships` the list of operators, on both sides. So a relationship the
+exponents refuse is not among the ones there are to write, in either target, and the table below is
+simply what neither writes. C# additionally reports each one as SEM008, having somewhere to report
+it to; C++ prints them.
+
+The two sides still differ in how many operators one relationship becomes, and that is the language
+rather than the physics: the vocabulary states each relationship once, in the direction the metadata
+declares it, and the C# generator expands it into the declared direction, its commutation and the
+divisions that undo it, because a caller who writes `duration * velocity` is not making a different
+claim. That expansion lives in `QuantitiesGenerator.CollectOperators`.
 
 | Refused | Why |
 |---|---|
@@ -289,7 +297,7 @@ var converted = sourceString.As<SourceType, TargetType>();
   - **SEM005** — schema-level validation issue in `logarithmic.json` (missing or duplicate scale names, a conversion with no linear type).
   - **SEM006** — a metadata file a generator declared in `MetadataFileNames` was not supplied as an `AdditionalFile`. Previously this produced no output and no explanation, which is indistinguishable from a generator that simply had nothing to emit.
   - **SEM007** — a metadata file could not be parsed. Replaces the base generator's `CONV001` in category `SourceGenerator`, and covers the path that used to swallow the exception, where a malformed `units.json` silently produced factories with no scale factor.
-  - **SEM008** — a relationship's declared result does not follow from the dimensions of its operands, or its value is signed and the declared result is a magnitude. The check comes from `Semantics.Vocabulary`, shared with the C++ projection; before that this side checked the names (SEM001) and the forms (SEM003) and then emitted the operator, so `Sensitivity * Pressure -> ElectricPotential` shipped as a working C# operator computing the wrong physics — which is what found that bug, and it is now fixed. The operator is **still emitted** for the four that remain, because dropping one would be a breaking change to a shipped package. Suppressed in `Semantics.Quantities.csproj` because ktsu.Sdk builds warnings as errors and those four are outstanding; `UnkeepableRelationshipTests` pins the set so a fifth fails there rather than disappearing into the suppression.
+  - **SEM008** — a relationship's declared result does not follow from the dimensions of its operands, or its value is signed and the declared result is a magnitude. The check comes from `Semantics.Vocabulary`, shared with the C++ projection; before that this side checked the names (SEM001) and the forms (SEM003) and then emitted the operator, so `Sensitivity * Pressure -> ElectricPotential` shipped as a working C# operator computing the wrong physics — which is what found that bug, and it is now fixed. **No operator is generated** for a refused relationship, in any of the directions C# spells a product in — that followed from making the vocabulary drive emission rather than only check it, and the removal is documented in `docs/migration-guide-5.0.md`. Suppressed in `Semantics.Quantities.csproj` because ktsu.Sdk builds warnings as errors and the four below are outstanding; `UnkeepableRelationshipTests` pins the set, and asserts that none of them is in the compiled surface, so a fifth fails there rather than disappearing into the suppression.
   - Descriptors are allocated from `SemanticsDiagnostics`, which is the one place to add a new one. `AnalyzerReleaseTrackingTests` fails if the identifier is missing from `AnalyzerReleases.Unshipped.md`, so RS2008 no longer surfaces only after a push.
 - See `docs/physics-generator.md` for the full schema and an end-to-end "add a dimension" walk-through.
 
@@ -304,3 +312,5 @@ This file is the entry point. For deeper material:
 - `docs/migration-guide-2.0.md` — 1.x → 2.0 upgrade guide (renames, namespace moves, behavioral changes).
 - `docs/migration-guide-3.0.md` — 2.x → 3.0 upgrade guide (removed first-class .NET type attributes, chord flag enum renames).
 - `docs/migration-guide-3.1.md` — 3.0 → 3.1 upgrade guide (JSON converter is now opt-in, `PhysicalConstants` domain fields became generic accessors).
+- `docs/migration-guide-4.0.md` — 3.x → 4.0 upgrade guide (every quantity became a `readonly record struct`).
+- `docs/migration-guide-5.0.md` — 4.x → 5.0 upgrade guide (the four dimensionally unkeepable relationships no longer generate operators).

Semantics.Cpp/MetadataProjection.cs

@@ -41,8 +41,10 @@ [.. dimension.DotProducts.Select(Relationship)],
 	// A constraint is carried as the flag the vocabulary reads rather than as its value: only a
 	// strict-positive floor is declared anywhere, and what the vocabulary needs is whether it is
 	// there. The value itself is the C# generator's business, which is where the guard is emitted.
+	// Read off the constraint's value rather than off the presence of the object holding it, so a
+	// constraint of some other kind, when one is added, does not silently turn the strict floor on.
 	private static OverloadDeclaration Overload(MetadataOverload overload) =>
-		new(overload.Name, overload.Description, overload.PhysicalConstraints is not null);
+		new(overload.Name, overload.Description, overload.PhysicalConstraints?.MinExclusive == "0");
 
 	private static RelationshipDeclaration Relationship(MetadataRelationship relationship) =>
 		new(relationship.Other, relationship.Result, [.. relationship.Forms]);

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/Angle.g.cs

@@ -159,11 +159,5 @@ namespace ktsu.Semantics.Quantities;
 	/// </summary>
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static Duration<T> operator /(Angle<T> left, AngularSpeed<T> right) => Duration<T>.Create(left.Quantity / right.Quantity);
-
-	/// <summary>
-	/// Multiplies Angle by TorqueMagnitude to produce Energy.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static Energy<T> operator *(Angle<T> left, TorqueMagnitude<T> right) => Energy<T>.Create(left.Quantity * right.Quantity);
 }
 

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/AngularAccelerationMagnitude.g.cs

@@ -133,11 +133,5 @@ namespace ktsu.Semantics.Quantities;
 	/// </summary>
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static Duration<T> operator /(AngularAccelerationMagnitude<T> left, AngularJerkMagnitude<T> right) => Duration<T>.Create(left.Quantity / right.Quantity);
-
-	/// <summary>
-	/// Multiplies AngularAccelerationMagnitude by MomentOfInertia to produce TorqueMagnitude.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static TorqueMagnitude<T> operator *(AngularAccelerationMagnitude<T> left, MomentOfInertia<T> right) => TorqueMagnitude<T>.Create(left.Quantity * right.Quantity);
 }
 

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/AngularMomentumMagnitude.g.cs

@@ -121,17 +121,5 @@ namespace ktsu.Semantics.Quantities;
 	/// </summary>
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static TorqueMagnitude<T> operator /(AngularMomentumMagnitude<T> left, Duration<T> right) => TorqueMagnitude<T>.Create(left.Quantity / right.Quantity);
-
-	/// <summary>
-	/// Divides AngularMomentumMagnitude by AngularSpeed to produce MomentOfInertia.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static MomentOfInertia<T> operator /(AngularMomentumMagnitude<T> left, AngularSpeed<T> right) => MomentOfInertia<T>.Create(left.Quantity / right.Quantity);
-
-	/// <summary>
-	/// Divides AngularMomentumMagnitude by MomentOfInertia to produce AngularSpeed.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static AngularSpeed<T> operator /(AngularMomentumMagnitude<T> left, MomentOfInertia<T> right) => AngularSpeed<T>.Create(left.Quantity / right.Quantity);
 }
 

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/AngularSpeed.g.cs

@@ -141,11 +141,5 @@ namespace ktsu.Semantics.Quantities;
 	/// </summary>
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static Duration<T> operator /(AngularSpeed<T> left, AngularAccelerationMagnitude<T> right) => Duration<T>.Create(left.Quantity / right.Quantity);
-
-	/// <summary>
-	/// Multiplies AngularSpeed by MomentOfInertia to produce AngularMomentumMagnitude.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static AngularMomentumMagnitude<T> operator *(AngularSpeed<T> left, MomentOfInertia<T> right) => AngularMomentumMagnitude<T>.Create(left.Quantity * right.Quantity);
 }
 

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/Energy.g.cs

@@ -180,18 +180,6 @@ namespace ktsu.Semantics.Quantities;
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static Energy<T> operator -(Energy<T> left, Energy<T> right) => Create(T.Abs(left.Quantity - right.Quantity));
 
-	/// <summary>
-	/// Divides Energy by Angle to produce TorqueMagnitude.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static TorqueMagnitude<T> operator /(Energy<T> left, Angle<T> right) => TorqueMagnitude<T>.Create(left.Quantity / right.Quantity);
-
-	/// <summary>
-	/// Divides Energy by TorqueMagnitude to produce Angle.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static Angle<T> operator /(Energy<T> left, TorqueMagnitude<T> right) => Angle<T>.Create(left.Quantity / right.Quantity);
-
 	/// <summary>
 	/// Divides Energy by Length to produce ForceMagnitude.
 	/// </summary>

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/Force2D.g.cs

@@ -96,7 +96,4 @@ public Force2D<T> Normalize()
 	/// <summary>Force2D * Duration = Momentum2D.</summary>
 	public static Momentum2D<T> operator *(Force2D<T> left, Duration<T> right) => new() { X = left.X * right.Value, Y = left.Y * right.Value };
 
-	/// <summary>Typed dot product: Force2D . Displacement2D = Energy.</summary>
-	public Energy<T> Dot(Displacement2D<T> other) => Energy<T>.Create((X * other.X) + (Y * other.Y));
-
 };

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/Force3D.g.cs

@@ -110,7 +110,4 @@ public Force3D<T> Normalize()
 	/// <summary>Force3D * Duration = Momentum3D.</summary>
 	public static Momentum3D<T> operator *(Force3D<T> left, Duration<T> right) => new() { X = left.X * right.Value, Y = left.Y * right.Value, Z = left.Z * right.Value };
 
-	/// <summary>Typed dot product: Force3D . Displacement3D = Energy.</summary>
-	public Energy<T> Dot(Displacement3D<T> other) => Energy<T>.Create((X * other.X) + (Y * other.Y) + (Z * other.Z));
-
 };

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/Force4D.g.cs

@@ -112,7 +112,4 @@ public Force4D<T> Normalize()
 	/// <summary>Force4D * Duration = Momentum4D.</summary>
 	public static Momentum4D<T> operator *(Force4D<T> left, Duration<T> right) => new() { X = left.X * right.Value, Y = left.Y * right.Value, Z = left.Z * right.Value, W = left.W * right.Value };
 
-	/// <summary>Typed dot product: Force4D . Displacement4D = Energy.</summary>
-	public Energy<T> Dot(Displacement4D<T> other) => Energy<T>.Create((X * other.X) + (Y * other.Y) + (Z * other.Z) + (W * other.W));
-
 };

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/MomentOfInertia.g.cs

@@ -115,17 +115,5 @@ namespace ktsu.Semantics.Quantities;
 	/// </summary>
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static MomentOfInertia<T> operator -(MomentOfInertia<T> left, MomentOfInertia<T> right) => Create(T.Abs(left.Quantity - right.Quantity));
-
-	/// <summary>
-	/// Multiplies MomentOfInertia by AngularSpeed to produce AngularMomentumMagnitude.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static AngularMomentumMagnitude<T> operator *(MomentOfInertia<T> left, AngularSpeed<T> right) => AngularMomentumMagnitude<T>.Create(left.Quantity * right.Quantity);
-
-	/// <summary>
-	/// Multiplies MomentOfInertia by AngularAccelerationMagnitude to produce TorqueMagnitude.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static TorqueMagnitude<T> operator *(MomentOfInertia<T> left, AngularAccelerationMagnitude<T> right) => TorqueMagnitude<T>.Create(left.Quantity * right.Quantity);
 }
 

Semantics.Quantities/Generated/Semantics.SourceGenerators/Semantics.SourceGenerators.QuantitiesGenerator/TorqueMagnitude.g.cs

@@ -124,28 +124,10 @@ namespace ktsu.Semantics.Quantities;
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static TorqueMagnitude<T> operator -(TorqueMagnitude<T> left, TorqueMagnitude<T> right) => Create(T.Abs(left.Quantity - right.Quantity));
 
-	/// <summary>
-	/// Multiplies TorqueMagnitude by Angle to produce Energy.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static Energy<T> operator *(TorqueMagnitude<T> left, Angle<T> right) => Energy<T>.Create(left.Quantity * right.Quantity);
-
 	/// <summary>
 	/// Multiplies TorqueMagnitude by Duration to produce AngularMomentumMagnitude.
 	/// </summary>
 	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
 	public static AngularMomentumMagnitude<T> operator *(TorqueMagnitude<T> left, Duration<T> right) => AngularMomentumMagnitude<T>.Create(left.Quantity * right.Quantity);
-
-	/// <summary>
-	/// Divides TorqueMagnitude by AngularAccelerationMagnitude to produce MomentOfInertia.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static MomentOfInertia<T> operator /(TorqueMagnitude<T> left, AngularAccelerationMagnitude<T> right) => MomentOfInertia<T>.Create(left.Quantity / right.Quantity);
-
-	/// <summary>
-	/// Divides TorqueMagnitude by MomentOfInertia to produce AngularAccelerationMagnitude.
-	/// </summary>
-	[System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2225:Operator overloads have named alternates", Justification = "Physics quantity operator")]
-	public static AngularAccelerationMagnitude<T> operator /(TorqueMagnitude<T> left, MomentOfInertia<T> right) => AngularAccelerationMagnitude<T>.Create(left.Quantity / right.Quantity);
 }
 

Semantics.Quantities/Semantics.Quantities.csproj

@@ -4,15 +4,17 @@
   <PropertyGroup>
     <TargetFrameworks>net10.0;net9.0;net8.0</TargetFrameworks>
     <!-- SEM008 reports a relationship in dimensions.json whose declared result does not follow
-         from its operands. Four are outstanding and all four are documented in CLAUDE.md: three are
-         the "r x F versus tau . theta" contradiction and are provably unfixable by choosing
-         exponents, and one needs a vector1 form on Energy. ktsu.Sdk builds warnings as errors, so
-         until those four are settled the diagnostic cannot be left on here.
+         from its operands, and no operator is generated for it. Four are outstanding and all four
+         are documented in CLAUDE.md: three are the "r x F versus tau . theta" contradiction and are
+         provably unfixable by choosing exponents, and one needs a vector1 form on Energy. ktsu.Sdk
+         builds warnings as errors, so until those four are settled the diagnostic cannot be left on
+         here.
          There were five. Sensitivity * Pressure to ElectricPotential was a plain metadata bug and is
          fixed, which is what this line is meant to make happen rather than hide.
          It is suppressed only in this project, so a consumer editing metadata still sees it, and
-         UnkeepableRelationshipTests pins the set to exactly those four: a fifth fails there rather
-         than disappearing into this line. Delete this when dimensions.json is fixed. -->
+         UnkeepableRelationshipTests pins the set to exactly those four — and asserts that none of
+         them is in the compiled surface — so a fifth fails there rather than disappearing into this
+         line. Delete this when dimensions.json is fixed. -->
     <NoWarn>$(NoWarn);CA1716;CA2225;KTSU0003;IDE0032;SEM008</NoWarn>
     <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
     <CompilerGeneratedFilesOutputPath>Generated</CompilerGeneratedFilesOutputPath>