feat: improve grouping perf in edgeless (#14442)

fix #14433 

#### PR Dependency Tree


* **PR #14442** 👈

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**
  * Level-of-detail thumbnails for large images.
  * Adaptive pacing for snapping, distribution and other alignment work.
  * RAF coalescer utility to batch high-frequency updates.
  * Operation timing utility to measure synchronous work.

* **Improvements**
* Batch group/ungroup reparenting that preserves element order and
selection.
  * Coalesced panning and drag updates to reduce jitter.
* Connector/group indexing for more reliable updates, deletions and
sync.
  * Throttled viewport refresh behavior.

* **Documentation**
  * Docs added for RAF coalescer and measureOperation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/integration-test/src/__tests__/edgeless/surface-model.spec.ts

@@ -235,6 +235,69 @@ describe('connector', () => {
     expect(model.getConnectors(id2)).toEqual([]);
   });
 
+  test('should update endpoint index when connector retargets', () => {
+    const id = model.addElement({
+      type: 'shape',
+    });
+    const id2 = model.addElement({
+      type: 'shape',
+    });
+    const id3 = model.addElement({
+      type: 'shape',
+    });
+    const connectorId = model.addElement({
+      type: 'connector',
+      source: {
+        id,
+      },
+      target: {
+        id: id2,
+      },
+    });
+    const connector = model.getElementById(connectorId)!;
+
+    expect(model.getConnectors(id).map(c => c.id)).toEqual([connector.id]);
+    expect(model.getConnectors(id2).map(c => c.id)).toEqual([connector.id]);
+
+    model.updateElement(connectorId, {
+      source: {
+        id: id3,
+      },
+      target: {
+        id: id2,
+      },
+    });
+
+    expect(model.getConnectors(id)).toEqual([]);
+    expect(model.getConnectors(id3).map(c => c.id)).toEqual([connector.id]);
+    expect(model.getConnectors(id2).map(c => c.id)).toEqual([connector.id]);
+  });
+
+  test('getConnectors should purge stale connector ids from endpoint cache', () => {
+    const shapeId = model.addElement({
+      type: 'shape',
+    });
+    const surfaceModel = model as any;
+    surfaceModel._connectorIdsByEndpoint.set(
+      shapeId,
+      new Set(['missing-connector-id'])
+    );
+    surfaceModel._connectorEndpoints.set('missing-connector-id', {
+      sourceId: shapeId,
+      targetId: null,
+    });
+
+    expect(model.getConnectors(shapeId)).toEqual([]);
+    expect(
+      surfaceModel._connectorIdsByEndpoint
+        .get(shapeId)
+        ?.has('missing-connector-id') ?? false
+    ).toBe(false);
+    expect(surfaceModel._connectorEndpoints.has('missing-connector-id')).toBe(
+      false
+    );
+  });
+
   test('should return null if connector are deleted', async () => {
     const id = model.addElement({
       type: 'shape',