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-git-changes-tab.tsx

@@ -615,8 +615,23 @@ export function GitChangesTab() {
     if (!rootPath || !isChangesTabActive) 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 scheduleRefresh = () => {
       if (refreshTimerRef.current) {
         clearTimeout(refreshTimerRef.current)
@@ -629,12 +644,17 @@ export function GitChangesTab() {
     const setup = async () => {
       try {
         await startFileTreeWatch(rootPath)
+        watchStarted = true
       } catch {
         // ignore watch startup errors
       }
+      if (disposed) {
+        releaseWatch()
+        return
+      }
 
       try {
-        unlisten = await subscribe<FileTreeChangedEvent>(
+        const subscribedUnlisten = await subscribe<FileTreeChangedEvent>(
           "folder://file-tree-changed",
           (payload) => {
             if (
@@ -646,6 +666,12 @@ export function GitChangesTab() {
             scheduleRefresh()
           }
         )
+        if (disposed) {
+          subscribedUnlisten()
+          releaseWatch()
+          return
+        }
+        unlisten = subscribedUnlisten
       } catch {
         // ignore listen errors
       }
@@ -654,12 +680,12 @@ export function GitChangesTab() {
     void setup()
 
     return () => {
+      disposed = true
       if (refreshTimerRef.current) {
         clearTimeout(refreshTimerRef.current)
         refreshTimerRef.current = null
       }
-      unlisten?.()
-      void stopFileTreeWatch(rootPath)
+      releaseWatch()
     }
   }, [fetchChanges, folder?.path, isChangesTabActive])