fix(editor): at-menu boundary in chat pannel (#13241)

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[BS-3621](https://linear.app/affine-design/issue/BS-3621/comment-menu-需要规避边缘)

#### PR Dependency Tree


* **PR #13241** 👈

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

* **Bug Fixes**
* Improved the positioning of the linked document popover to ensure it
displays correctly, even when its width is not initially rendered.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->


#### PR Dependency Tree


* **PR #13241** 👈

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

blocksuite/affine/widgets/linked-doc/src/linked-doc-popover.ts

@@ -343,7 +343,18 @@ export class LinkedDocPopover extends SignalWatcher(
   override willUpdate() {
     if (!this.hasUpdated) {
       const updatePosition = throttle(() => {
-        this._position = getPopperPosition(this, this.context.startNativeRange);
+        this._position = getPopperPosition(
+          {
+            getBoundingClientRect: () => {
+              return {
+                ...this.getBoundingClientRect(),
+                // Workaround: the width of the popover is zero when it is not rendered
+                width: 280,
+              };
+            },
+          },
+          this.context.startNativeRange
+        );
       }, 10);
 
       this.disposables.addFromEvent(window, 'resize', updatePosition);