fix(workspace-state): stop resync loop on non-git folders and allow retry for degraded watcher

Gate git refresh on .git presence so file churn in non-git workspaces no longer produces endless resync_hint events, and silently log tree/git refresh errors during watch flushing instead of flagging requires_resync, which turned transient failures into self-reinforcing loops.

Degrade gracefully when the filesystem watcher fails to attach (e.g. permission denied, inotify quota): keep the initial snapshot, surface a degraded flag, and expose a store-level restart that the banner uses to retry attachment after the root cause is fixed.

Propagate is_git_repo through the snapshot so the git log and changes tabs render a dedicated "Not a Git repository" empty state instead of raw git stderr with a useless retry button.

Stop polling get_git_branch from the title bar once it returns null and re-arm on visibility change.

Add translations for the new banner, empty-state, and retry keys across all ten locales.

src/i18n/messages/zh-TW.json

@@ -769,6 +769,12 @@
     "applyRightNonConflicting": "套用遠端"
   },
   "Folder": {
+    "workspaceStatus": {
+      "degradedTitle": "即時更新不可用",
+      "degradedHint": "監聽器啟動失敗（如目錄無讀取權限）。請手動重新整理以取得最新變更。",
+      "retry": "重試",
+      "retrying": "重試中..."
+    },
     "common": {
       "all": "全部",
       "cancel": "取消",
@@ -1205,6 +1211,8 @@
       "workspace": "工作區",
       "retry": "重試",
       "noCommitsFound": "未找到提交記錄",
+      "notAGitRepoTitle": "不是 Git 儲存庫",
+      "notAGitRepoHint": "可從上方分支選單初始化 Git，或開啟已有的 Git 儲存庫。",
       "hash": "Hash",
       "copyHash": "複製雜湊",
       "copyMessage": "複製提交訊息",
@@ -1281,6 +1289,8 @@
     "gitChangesTab": {
       "workspace": "工作區",
       "noChanges": "暫無本地變更",
+      "notAGitRepoTitle": "不是 Git 儲存庫",
+      "notAGitRepoHint": "可從上方分支選單初始化 Git，或開啟已有的 Git 儲存庫。",
       "trackedChanges": "本地已追蹤變更 ({count})",
       "untrackedFiles": "本地未追蹤檔案 ({count})",
       "expandTracked": "展開已追蹤變更",