fix(skill): address code review issues for tab management

1. Add confirmation dialog when closing dirty tabs
2. Fix file double-click race condition with useDelayedClick hook
3. Fix previewTabId orphan state in closeTab
4. Remove auto-pin on every keystroke (VS Code behavior)
5. Extract shared MenuItem component to eliminate duplication
6. Make nodeId optional when node is provided (reduce props drilling)

web/i18n/en-US/workflow.json

@@ -1031,6 +1031,9 @@
   "skillSidebar.newFolder": "New folder",
   "skillSidebar.searchPlaceholder": "Search files…",
   "skillSidebar.toggleFolder": "Toggle folder",
+  "skillSidebar.unsavedChanges.confirmClose": "Discard",
+  "skillSidebar.unsavedChanges.content": "You have unsaved changes. Do you want to discard them?",
+  "skillSidebar.unsavedChanges.title": "Unsaved changes",
   "skillSidebar.uploading": "Uploading…",
   "tabs.-": "Default",
   "tabs.addAll": "Add all",

web/i18n/zh-Hans/workflow.json

@@ -1023,6 +1023,9 @@
   "skillSidebar.menu.uploadFolder": "上传文件夹",
   "skillSidebar.newFolder": "新建文件夹",
   "skillSidebar.searchPlaceholder": "搜索文件...",
+  "skillSidebar.unsavedChanges.confirmClose": "放弃",
+  "skillSidebar.unsavedChanges.content": "您有未保存的更改，是否放弃？",
+  "skillSidebar.unsavedChanges.title": "未保存的更改",
   "skillSidebar.uploading": "上传中...",
   "tabs.-": "默认",
   "tabs.addAll": "添加全部",