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/components/layout/workspace-degraded-banner.tsx

@@ -0,0 +1,59 @@
+"use client"
+
+import { useState } from "react"
+import { RefreshCw, TriangleAlert } from "lucide-react"
+import { useTranslations } from "next-intl"
+import { Button } from "@/components/ui/button"
+
+interface WorkspaceDegradedBannerProps {
+  onRetry?: () => void | Promise<void>
+}
+
+export function WorkspaceDegradedBanner({
+  onRetry,
+}: WorkspaceDegradedBannerProps) {
+  const t = useTranslations("Folder.workspaceStatus")
+  const [retrying, setRetrying] = useState(false)
+
+  const handleRetry = async () => {
+    if (!onRetry || retrying) return
+    setRetrying(true)
+    try {
+      await onRetry()
+    } finally {
+      setRetrying(false)
+    }
+  }
+
+  return (
+    <div
+      className="flex items-start gap-2 px-2 py-1.5 text-[11px] text-amber-700 dark:text-amber-400 bg-amber-100/60 dark:bg-amber-900/20 border-b border-amber-300/50 dark:border-amber-800/50"
+      role="status"
+      aria-live="polite"
+      title={t("degradedHint")}
+    >
+      <TriangleAlert className="size-3.5 mt-0.5 shrink-0" aria-hidden />
+      <div className="leading-snug flex-1">
+        <span className="font-medium">{t("degradedTitle")}</span>
+        <span className="ml-1 text-muted-foreground">{t("degradedHint")}</span>
+      </div>
+      {onRetry && (
+        <Button
+          variant="ghost"
+          size="xs"
+          className="h-5 px-1.5 -my-0.5 shrink-0 text-amber-700 dark:text-amber-400 hover:bg-amber-200/60 dark:hover:bg-amber-900/40"
+          onClick={() => {
+            void handleRetry()
+          }}
+          disabled={retrying}
+        >
+          <RefreshCw
+            className={`size-3 ${retrying ? "animate-spin" : ""}`}
+            aria-hidden
+          />
+          <span className="ml-1">{retrying ? t("retrying") : t("retry")}</span>
+        </Button>
+      )}
+    </div>
+  )
+}