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/affine/model/src/elements/connector/connector.ts

@@ -177,6 +177,11 @@ export class ConnectorElementModel extends GfxPrimitiveElementModel<ConnectorEle
   override getNearestPoint(point: IVec): IVec {
     const { mode, absolutePath: path } = this;
 
+    if (path.length === 0) {
+      const { x, y } = this;
+      return [x, y];
+    }
+
     if (mode === ConnectorMode.Straight) {
       const first = path[0];
       const last = path[path.length - 1];
@@ -213,6 +218,10 @@ export class ConnectorElementModel extends GfxPrimitiveElementModel<ConnectorEle
       h = bounds.h;
     }
 
+    if (path.length === 0) {
+      return 0.5;
+    }
+
     point[0] = Vec.clamp(point[0], x, x + w);
     point[1] = Vec.clamp(point[1], y, y + h);
 
@@ -258,6 +267,10 @@ export class ConnectorElementModel extends GfxPrimitiveElementModel<ConnectorEle
       h = bounds.h;
     }
 
+    if (path.length === 0) {
+      return [x + w / 2, y + h / 2];
+    }
+
     if (mode === ConnectorMode.Orthogonal) {
       const points = path.map<IVec>(p => [p[0], p[1]]);
       const point = Polyline.pointAt(points, offsetDistance);
@@ -300,6 +313,10 @@ export class ConnectorElementModel extends GfxPrimitiveElementModel<ConnectorEle
 
     const { mode, strokeWidth, absolutePath: path } = this;
 
+    if (path.length === 0) {
+      return false;
+    }
+
     const point =
       mode === ConnectorMode.Curve
         ? getBezierNearestPoint(getBezierParameters(path), currentPoint)