fix: preserve prototype getter/setter in property instrumentation

LGraphNodeProperties was shadowing LGraphNode's prototype shape
getter/setter with a closure-based own accessor. This caused
node.shape assignments to store values in a closure variable
instead of node._shape, making renderingShape always fall back
to the default round shape.

Skip instrumentation when a prototype accessor already exists,
since the prototype setter already emits change events.

Fixes #8532

src/lib/litegraph/src/LGraphNodeProperties.test.ts

@@ -68,6 +68,37 @@ describe('LGraphNodeProperties', () => {
     })
   })
 
+  describe('prototype accessor preservation', () => {
+    it('should not shadow prototype getter/setter with closure-based accessor', () => {
+      // Mirrors LGraphNode.shape / _shape pattern
+      class NodeWithShape {
+        _shape: number | undefined = undefined
+        id = 1
+        flags = {}
+        graph = mockGraph
+        title = 'test'
+        get shape(): number | undefined {
+          return this._shape
+        }
+        set shape(v: number) {
+          this._shape = v
+        }
+      }
+
+      const node = new NodeWithShape()
+      new LGraphNodeProperties(node as Partial<LGraphNode> as LGraphNode)
+
+      // The prototype getter/setter should NOT be shadowed
+      expect(Object.prototype.hasOwnProperty.call(node, 'shape')).toBe(false)
+
+      // Before fix: the closure-based accessor would shadow the prototype,
+      // storing the value in a closure and leaving _shape unchanged.
+      node.shape = 42
+      expect(node._shape).toBe(42)
+      expect(node.shape).toBe(42)
+    })
+  })
+
   describe('isTracked', () => {
     it('should correctly identify tracked properties', () => {
       const propManager = new LGraphNodeProperties(mockNode)

src/lib/litegraph/src/LGraphNodeProperties.ts

@@ -89,6 +89,16 @@ export class LGraphNodeProperties {
     const currentValue = targetObject[propertyName]
 
     if (!hasProperty) {
+      // Check if a prototype in the chain defines a getter/setter for this
+      // property.  Defining an own closure-based accessor would shadow the
+      // prototype accessor and break its internal logic (e.g. the `shape`
+      // setter that writes `_shape`).  Skip instrumentation in that case –
+      // the prototype setter is expected to emit its own change events.
+      if (this._hasPrototypeAccessor(targetObject, propertyName)) {
+        this._instrumentedPaths.add(path)
+        return
+      }
+
       let value: unknown = undefined
 
       Object.defineProperty(targetObject, propertyName, {
@@ -128,6 +138,23 @@ export class LGraphNodeProperties {
     this._instrumentedPaths.add(path)
   }
 
+  /**
+   * Checks whether any prototype in the chain defines a getter/setter for
+   * the given property.
+   */
+  private _hasPrototypeAccessor(
+    obj: Record<string, unknown>,
+    propertyName: string
+  ): boolean {
+    let proto = Object.getPrototypeOf(obj)
+    while (proto) {
+      const desc = Object.getOwnPropertyDescriptor(proto, propertyName)
+      if (desc && (desc.get || desc.set)) return true
+      proto = Object.getPrototypeOf(proto)
+    }
+    return false
+  }
+
   /**
    * Creates a property descriptor that emits change events
    */