Bind a node's border weight

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0147gqWiq3xoEdAGwWSpq9JK

Author: claude

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Unreleased
 
+- `strokeWeight` is a bindable style property of every node with strokes.
 - A navigate-back (`pop`) action reads from JSON without `destinationId`,
   which it has no use for. It is still written, as `''`, for readers that
   require it.

lib/src/api/mixins.dart

@@ -1045,8 +1045,8 @@ mixin PropertyVariableMixin on BaseNode {
   /// Properties of the node that can be used in actions or can be changed by
   /// an action.
   ///
-  /// Style properties (fill, stroke, opacity, width, height, flex; a text's
-  /// fill is its color) can be set by
+  /// Style properties (fill, stroke, strokeWeight, opacity, width, height,
+  /// flex; a text's fill is its color) can be set by
   /// conditions, bound to variables or formulas, or changed by a set value
   /// action, on any node that has them.
   late final List<ValueModel> propertyVariables = [
@@ -1055,6 +1055,8 @@ mixin PropertyVariableMixin on BaseNode {
     if (this case final GeometryMixin geometry) ...[
       PaintValue(name: 'fill', value: geometry.fills.firstOrNull),
       PaintValue(name: 'stroke', value: geometry.strokes.firstOrNull),
+      // A border that thickens when selected or hovered.
+      DoubleValue(name: 'strokeWeight', value: geometry.strokeWeight),
     ],
     if (this case final TextNode text)
       PaintValue(