Fix Move Diagrams to Separate File and Model Browser restore

[robertmclaws]

Move Diagrams to Separate File

• Resolved the project from the artifact instead of the Solution Explorer selection — ItemOperations.AddExistingItem threw when invoked from anywhere else
• Diagram file now nests under the EDMX, matching how the shipping designer records it
• Skips the add for Misc Files and already-globbed SDK-style projects; logs and continues if the project system refuses
• Captured the document name before migrating — the reload resets the current context, so CurrentDocData came back null on the save
• Replaced a Debug.Assert and an unchecked cast with real guards; both were live NREs in Release
• Guarded IsLinkProjectItem against project items exposing no DTE properties

Designer surface context menu

• Added the command under Show Data Types, using KnownMonikers.MoveToFolder
• Hidden once the diagrams already live in a .edmx.diagram file
• Shares one eligibility predicate and one execution path with the Model Browser command, so the two can't disagree

Model Browser startup exception

• Marked the tool window transient so the shell stops restoring a frame ModelingPackage cannot resolve
• EntityDesignExplorerWindow is a shell ToolWindowPane; the DSL registry that CreateToolWindow reads is typed to DSL ToolWindow, so its slot can never be registered
• Behaviour change: the window no longer reappears docked at startup. It previously did, as an exception box that was dead until a model loaded
• specs/model-browser-toolwindow-restore.md records the four approaches ruled out against the compiler, and the IVsPackage.CreateTool route if restore-at-startup is ever needed

Tests

• 3 tests, each mutation-checked by reverting its fix and confirming it fails
• A 4th was written and deleted: it passed with the guard removed, and reached VsUtils.ShowMessageBox, which degrades to a blocking modal dialog with no shell — it would have hung CI rather than failed
• The migration, status handler and tool window restore need the Exp hive; verification steps are in the spec

🤖 Generated with Claude Code