Salvaged from #32340 by @LeonSGP43, adapted to the workspace-scoped
status tracking that landed in #63709:
- /stop with no running agent now best-effort clears the platform
status indicator, so a phantom 'is thinking...' left by a gateway
restart or a turn that died without a final send can always be
dismissed (#32295).
- SlackAdapter.stop_typing clears an untracked thread when the caller
names it explicitly in metadata — clearing an unset status is a
harmless no-op on Slack's side. The fallback is skipped when multiple
Slack Connect workspaces track the same channel+thread and no team_id
is given, preserving #63709's cross-workspace safety guarantee.
dbd8704673