feat(ui): warn when the running worker predates the selected repo's merged HEAD

Stamps ClaudeDo.Worker's build with its exact git SHA (SourceRevisionId ->
InformationalVersion) and exposes it via a new GetWorkerBuildInfo hub call.
For the currently selected list, the shell compares that SHA against the
list's git HEAD (GitService.IsAncestorAsync) and shows a persistent footer
banner -- never auto-clearing, never shown on an unrelated repo or when the
ancestry can't be determined -- so "verified against a merge" claims aren't
silently made against a stale process. No auto-restart; the banner just
offers the existing RestartWorkerCommand.

src/ClaudeDo.Localization/locales/en.json

@@ -648,6 +648,9 @@
       "available": "Update available: v",
       "updateNow": "Update now",
       "dismiss": "Dismiss"
+    },
+    "staleWorker": {
+      "message": "The worker is running an older build than this repo's merged main — restart it so your merged changes take effect."
     }
   },
   "vm": {