feat(editor): improve edgeless perf & memory usage (#14591)

#### PR Dependency Tree


* **PR #14591** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* New canvas renderer debug metrics and controls for runtime inspection.
* Mindmap/group reordering now normalizes group targets, improving
reorder consistency.

* **Bug Fixes**
  * Fixed connector behavior for empty/degenerate paths.
* More aggressive viewport invalidation so structural changes display
correctly.
* Improved z-index synchronization during transforms and layer updates.

* **Performance**
* Retained DOM caching for brushes, shapes, and connectors to reduce DOM
churn.
* Targeted canvas refreshes, pooling, and reuse to lower redraw and
memory overhead.

* **Tests**
* Added canvas renderer performance benchmarks and curve edge-case unit
tests.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/framework/std/src/view/element/gfx-block-component.ts

@@ -31,6 +31,13 @@ function updateTransform(element: GfxBlockComponent) {
   element.style.transform = element.getCSSTransform();
 }
 
+function updateZIndex(element: GfxBlockComponent) {
+  const zIndex = element.toZIndex();
+  if (element.style.zIndex !== zIndex) {
+    element.style.zIndex = zIndex;
+  }
+}
+
 function updateBlockVisibility(view: GfxBlockComponent) {
   if (view.transformState$.value === 'active') {
     view.style.visibility = 'visible';
@@ -58,14 +65,22 @@ function handleGfxConnection(instance: GfxBlockComponent) {
     instance.store.slots.blockUpdated.subscribe(({ type, id }) => {
       if (id === instance.model.id && type === 'update') {
         updateTransform(instance);
+        updateZIndex(instance);
       }
     })
   );
 
+  instance.disposables.add(
+    instance.gfx.layer.slots.layerUpdated.subscribe(() => {
+      updateZIndex(instance);
+    })
+  );
+
   instance.disposables.add(
     effect(() => {
       updateBlockVisibility(instance);
       updateTransform(instance);
+      updateZIndex(instance);
     })
   );
 }