fix: remove redundant forceRender call and add ResizeObserver guard (#8372)

## Summary
- Remove duplicate forceRender() in ResizeObserver callback since
handleResize() already calls it
- Add guard for environments without ResizeObserver support
- Disconnect existing observer before reassigning to prevent leaks

requested by @DrJKL in
https://github.com/Comfy-Org/ComfyUI_frontend/pull/8351

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8372-fix-remove-redundant-forceRender-call-and-add-ResizeObserver-guard-2f66d73d3650811bb3a6de5c59b3c1fb)
by [Unito](https://www.unito.io)

src/extensions/core/load3d/Load3d.ts

@@ -157,9 +157,11 @@ class Load3d {
   }
 
   private initResizeObserver(container: Element | HTMLElement): void {
+    if (typeof ResizeObserver === 'undefined') return
+
+    this.resizeObserver?.disconnect()
     this.resizeObserver = new ResizeObserver(() => {
       this.handleResize()
-      this.forceRender()
     })
     this.resizeObserver.observe(container)
   }
@@ -522,7 +524,6 @@ class Load3d {
     this.viewHelperManager.recreateViewHelper()
 
     this.handleResize()
-    this.forceRender()
   }
 
   getCurrentCameraType(): 'perspective' | 'orthographic' {
@@ -584,7 +585,6 @@ class Load3d {
     }
 
     this.handleResize()
-    this.forceRender()
 
     this.loadingPromise = null
   }
@@ -618,7 +618,6 @@ class Load3d {
     this.targetHeight = height
     this.targetAspectRatio = width / height
     this.handleResize()
-    this.forceRender()
   }
 
   addEventListener<T>(event: string, callback: EventCallback<T>): void {
@@ -631,7 +630,6 @@ class Load3d {
 
   refreshViewport(): void {
     this.handleResize()
-    this.forceRender()
   }
 
   handleResize(): void {