fix(world): clean up dynamicAnchor listener on dispose (#767)

The dynamicAnchor setter never assigned _dynamicAnchor, so the getter always
returned false, and dispose never removed the pointerdown listener, keeping the
whole world alive (a leak visible on React remounts). Assign the flag and remove
the listener on dispose.

Co-authored-by: ShaMan123 <34343793+ShaMan123@users.noreply.github.com>

Author: ShaMan123

packages/core/src/core/Worlds/src/simple-world.ts

@@ -73,6 +73,7 @@ export class SimpleWorld<
     } else {
       container.removeEventListener("pointerdown", this.onPointerDown);
     }
+    this._dynamicAnchor = value;
   }
 
   get dynamicAnchor() {
@@ -234,6 +235,13 @@ export class SimpleWorld<
     this.enabled = false;
     this.isDisposing = true;
 
+    // Remove the dynamic anchoring listener before the renderer is disposed
+    const container = this.renderer?.three.domElement.parentElement;
+    if (container) {
+      container.removeEventListener("pointerdown", this.onPointerDown);
+    }
+    this._dynamicAnchor = false;
+
     this.scene.onWorldChanged.trigger({ world: this, action: "removed" });
     this.camera.onWorldChanged.trigger({ world: this, action: "removed" });
     if (this.renderer) {