fix(frontend): Drawer 焦点还原提取 useRestoreFocus + 回归测试 + DRY（CR-H11）

apps/web/components/workbench/ContextDrawer.tsx

@@ -8,6 +8,7 @@ import { ThinkingIndicator } from "@/components/ThinkingIndicator";
 import { Button } from "@/components/ui/Button";
 import { StatusNote } from "@/components/ui/StatusNote";
 import { handleTabTrap } from "@/lib/a11y/focusTrap";
+import { useRestoreFocus } from "@/lib/a11y/useRestoreFocus";
 import { useBodyScrollLock } from "@/lib/ui/useBodyScrollLock";
 import { badgeClass, cn, overlayScrim } from "@/lib/ui/variants";
 import {
@@ -45,20 +46,13 @@ export function ContextDrawer({
   const [activeTab, setActiveTab] = useState<ContextTabKey>("codex");
   const panelRef = useRef<HTMLDivElement>(null);
   const closeRef = useRef<HTMLButtonElement>(null);
-  const wasOpenRef = useRef(false);
   const data = useContextDrawerData(projectId, activeTab, open);
 
   useBodyScrollLock(open);
+  useRestoreFocus(open, triggerRef);
 
   useEffect(() => {
-    if (!open) {
-      if (wasOpenRef.current) {
-        wasOpenRef.current = false;
-        triggerRef?.current?.focus();
-      }
-      return;
-    }
-    wasOpenRef.current = true;
+    if (!open) return;
     const onKey = (e: KeyboardEvent): void => {
       if (e.key === "Escape") {
         e.preventDefault();
@@ -68,7 +62,7 @@ export function ContextDrawer({
     window.addEventListener("keydown", onKey);
     closeRef.current?.focus();
     return () => window.removeEventListener("keydown", onKey);
-  }, [open, onClose, triggerRef]);
+  }, [open, onClose]);
 
   if (!open) return null;