`onIssueLabelsChanged` patched the embedded `labels` field in the
issue list and detail caches but never touched `labelKeys.byIssue`,
the cache backing the issue-detail Properties LabelPicker. Mutations
already covered all three caches; WS-driven changes (agents, other
tabs) left the picker stale until remount, since `staleTime: Infinity`
plus `refetchOnWindowFocus: false` prevent recovery on focus.