fix(core): improve EdgelessCopilotPanel position (#11814)

Closes: [AF-2101](https://linear.app/affine-design/issue/AF-2101/ai-panel-的输入框menu定位错误，menu-应该出现在输入框下方)

[Screen Recording 2025-04-18 at 20.51.01.mov <span class="graphite__hidden">(uploaded via Graphite)</span> <img class="graphite__hidden" src="https://app.graphite.dev/api/v1/graphite/video/thumbnail/8ypiIKZXudF5a0tIgIzf/67410349-b056-40a7-b1e6-6de5a5137789.mov" />](https://app.graphite.dev/media/video/8ypiIKZXudF5a0tIgIzf/67410349-b056-40a7-b1e6-6de5a5137789.mov)

packages/frontend/core/src/blocksuite/ai/widgets/edgeless-copilot-panel/index.ts

@@ -15,14 +15,15 @@ export class EdgelessCopilotPanel extends WithDisposable(LitElement) {
     :host {
       display: flex;
       position: absolute;
+      max-height: 374px;
     }
 
     .edgeless-copilot-panel {
       box-sizing: border-box;
       padding: 8px 4px 8px 8px;
       min-width: 330px;
-      max-height: 374px;
       overflow-y: auto;
+      overscroll-behavior: contain;
       background: ${unsafeCSSVar('--affine-background-overlay-panel-color')};
       box-shadow: ${unsafeCSSVar('--affine-overlay-shadow')};
       border-radius: 8px;

packages/frontend/core/src/blocksuite/ai/widgets/edgeless-copilot/index.ts

@@ -11,9 +11,10 @@ import {
 import { WidgetComponent, WidgetViewExtension } from '@blocksuite/affine/std';
 import { GfxControllerIdentifier } from '@blocksuite/affine/std/gfx';
 import {
+  autoPlacement,
   autoUpdate,
   computePosition,
-  flip,
+  limitShift,
   offset,
   shift,
   size,
@@ -112,41 +113,43 @@ export class EdgelessCopilotWidget extends WidgetComponent<RootBlockModel> {
   }
 
   private _updateCopilotPanel(referenceElement: HTMLElement) {
-    // @TODO: optimize
-    const viewport = this.gfx.viewport;
     const panel = this._copilotPanel;
     if (!panel) return;
+
+    const originMaxHeight = window.getComputedStyle(panel).maxHeight;
+
     autoUpdate(referenceElement, panel, () => {
       computePosition(referenceElement, panel, {
         placement: 'bottom-start',
         middleware: [
-          offset({
-            mainAxis: 4,
-          }),
-          flip({
-            mainAxis: true,
-            crossAxis: true,
-            flipAlignment: true,
-          }),
-          shift(() => {
-            const { left, top, width, height } = viewport;
-            return {
-              padding: 20,
-              crossAxis: true,
-              rootBoundary: {
-                x: left,
-                y: top,
-                width,
-                height: height - 100,
-              },
-            };
+          offset(4),
+          autoPlacement({
+            padding: 10,
+            allowedPlacements: [
+              'top-start',
+              'top-end',
+              'bottom-start',
+              'bottom-end',
+            ],
           }),
           size({
-            apply: ({ elements }) => {
-              const { height } = viewport;
-              elements.floating.style.maxHeight = `${height - 140}px`;
+            apply: ({ availableHeight }) => {
+              availableHeight -= 10;
+              panel.style.maxHeight =
+                originMaxHeight && originMaxHeight !== 'none'
+                  ? `min(${originMaxHeight}, ${availableHeight}px)`
+                  : `${availableHeight}px`;
             },
           }),
+          shift({
+            padding: {
+              top: 10,
+              right: 10,
+              bottom: 150,
+              left: 10,
+            },
+            limiter: limitShift(),
+          }),
         ],
       })
         .then(({ x, y }) => {