fix: 约束 AGC 素材候选弹层到输入框范围

- 类型提示改为固定定位并按输入框宽度约束

- 根据上下可用空间选择展开方向

- 避免弹层越过聊天栏覆盖其它区域

apps/ai-game-creator-shell/src/features/project-workspace/ResourceReferenceInput.tsx

@@ -367,15 +367,48 @@ function ResourceReferenceEditor({
   );
 
   const renderMentionMenu: MenuRenderFn<ResourceMentionOption> = useCallback(
-    (anchorElementRef, itemProps) => {
-      if (!anchorElementRef.current || itemProps.options.length === 0) {
+    (_anchorElementRef, itemProps) => {
+      const inputRect = rootRef.current?.getBoundingClientRect();
+      if (!inputRect || itemProps.options.length === 0) {
         return null;
       }
+      const viewportPadding = 12;
+      const menuWidth = Math.min(
+        Math.max(280, inputRect.width),
+        Math.min(420, window.innerWidth - viewportPadding * 2),
+      );
+      const left = Math.min(
+        Math.max(viewportPadding, inputRect.left),
+        Math.max(
+          viewportPadding,
+          window.innerWidth - menuWidth - viewportPadding,
+        ),
+      );
+      const availableAbove = Math.max(0, inputRect.top - viewportPadding - 8);
+      const availableBelow = Math.max(
+        0,
+        window.innerHeight - inputRect.bottom - viewportPadding - 8,
+      );
+      const openAbove = availableBelow < 160 && availableAbove > availableBelow;
+      const maxHeight = Math.max(
+        120,
+        Math.min(240, openAbove ? availableAbove : availableBelow),
+      );
+      const top = openAbove
+        ? Math.max(viewportPadding, inputRect.top - maxHeight - 8)
+        : inputRect.bottom + 8;
       return createPortal(
         <div
           className="resource-reference-menu"
           role="listbox"
           aria-label="候选素材"
+          style={{
+            position: 'fixed',
+            top: `${top}px`,
+            left: `${left}px`,
+            width: `${menuWidth}px`,
+            maxHeight: `${maxHeight}px`,
+          }}
         >
           {itemProps.options.map((option, index) => (
             <button
@@ -396,7 +429,7 @@ function ResourceReferenceEditor({
             </button>
           ))}
         </div>,
-        anchorElementRef.current,
+        document.body,
       );
     },
     [],