fix(folder): prevent stale file watch subscriptions in aux tabs

Ensure async watch setup is safely discarded after effect cleanup.

Use idempotent watcher release logic to avoid duplicate subscriptions and unbalanced stop calls.

src/components/layout/aux-panel-file-tree-tab.tsx

@@ -1895,8 +1895,23 @@ export function FileTreeTab() {
     if (!rootPath) return
 
     let unlisten: (() => void) | null = null
+    let disposed = false
+    let watchStarted = false
+    let watchReleased = false
     const normalizedRootPath = normalizeComparePath(rootPath)
 
+    const releaseWatch = () => {
+      if (watchReleased) return
+      watchReleased = true
+      if (unlisten) {
+        unlisten()
+        unlisten = null
+      }
+      if (watchStarted) {
+        void stopFileTreeWatch(rootPath)
+      }
+    }
+
     const scheduleTreeRefresh = (refreshGitStatus: boolean) => {
       if (!isFileTreeTabActiveRef.current) {
         pendingTreeRefreshRef.current = true
@@ -2027,13 +2042,18 @@ export function FileTreeTab() {
     const setup = async () => {
       try {
         await startFileTreeWatch(rootPath)
+        watchStarted = true
       } catch (error) {
         const message = error instanceof Error ? error.message : String(error)
         toast.error(t("toasts.watchStartFailed"), { description: message })
       }
+      if (disposed) {
+        releaseWatch()
+        return
+      }
 
       try {
-        unlisten = await subscribe<FileTreeChangedEvent>(
+        const subscribedUnlisten = await subscribe<FileTreeChangedEvent>(
           "folder://file-tree-changed",
           (payload) => {
             if (
@@ -2109,6 +2129,12 @@ export function FileTreeTab() {
             })()
           }
         )
+        if (disposed) {
+          subscribedUnlisten()
+          releaseWatch()
+          return
+        }
+        unlisten = subscribedUnlisten
       } catch (error) {
         console.error("[FileTreeTab] failed to listen file watch event:", error)
       }
@@ -2117,6 +2143,7 @@ export function FileTreeTab() {
     void setup()
 
     return () => {
+      disposed = true
       if (treeRefreshTimerRef.current) {
         clearTimeout(treeRefreshTimerRef.current)
         treeRefreshTimerRef.current = null
@@ -2129,8 +2156,7 @@ export function FileTreeTab() {
       pendingTreeRefreshRef.current = false
       pendingTreeRefreshNeedsStatusRef.current = false
       pendingStatusRefreshRef.current = false
-      unlisten?.()
-      void stopFileTreeWatch(rootPath)
+      releaseWatch()
     }
   }, [fetchTree, folder?.path, openFilePreview, t])