POST /lifecycle/graceful-stop — request an orderly shutdown of THIS daemon

process, regardless of residency.

The true root cause this closes: on Windows, a caller-initiated restart (e.g. GUI settings-change restart in uc-desktop::daemon_probe::restart_local_daemon) has no real signal to send — TerminateProcess kills the process before its async graceful-shutdown task ever runs mark_clean_exit(), so the next boot logs a false "previous daemon run exited abnormally". This endpoint lets the caller ask first: the start marker is cleared HERE, synchronously, before the shutdown sequence even starts, so the marker is already correct even if the caller's graceful wait times out and it falls back to a hard kill.

Deliberately NOT routed through [RestartCoordinator] — that machinery is reserved for Oneshot-residency promotion (ADR-008 P5-L L8c) and refuses any other residency. This endpoint works for every residency and does not touch quiescing.