nisse-review: a stop ends a review in progress; quieter repo failures

SIGTERM used to stop only new rounds: a review in progress ran on until
systemd killed it 90s later. Now the scheduler's stop sets the driver's
cancel flag, so the run ends at its next turn, and a model call in flight
is broken off (Interruptible, raising Stopped from the signal handler, only
ever inside a model call). The item goes back to ready, with nothing
drafted posted and no failure counted; replies already posted carry their
markers and are not repeated.

intake.repo_failed is logged when a repository starts failing or the reason
changes, and intake.repo_ok when it lists again, not every round.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J5Utyfzw7gF7UhjRDEtjTk

nisse-review/src/nisse_review/main.py

@@ -26,7 +26,7 @@ def main() -> int:
 
     def shutdown(_signum: int, _frame: FrameType | None) -> None:
         print("nisse-review: stopping", file=sys.stderr)
-        built.scheduler.stop()
+        built.stop()
 
     signal.signal(signal.SIGINT, shutdown)
     signal.signal(signal.SIGTERM, shutdown)