nisse-review: a new head's review waits for its CI

A review judges the CI result (R1), so a new head's review now waits while
its checks are pending, and starts once they finish, passed or failed. It
also keeps reviews off a GPU that CI is using: #154's first review ran
beside CI's end-to-end job and took about 30 minutes.

- Pending: waits up to tuning.review.ci_wait_s (1 h), then reviews anyway.
- No checks: waits tuning.review.ci_grace_s (2 min) for them to appear,
  then reviews.
- A PR waiting on CI holds up no other: the oldest settled one goes first.
- The head's first sighting is kept on the item (seen_at).

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/config.py

@@ -55,6 +55,10 @@ class ReviewTuning:
     max_turns: int = 40  # a review run's turn cap
     diff_chars: int = 60000  # the diff in the review's context; files on demand
     attempts: int = 2  # failed runs on one PR before saying so on it
+    # A new head waits for its CI to finish: at most ci_wait_s while checks
+    # are pending, and ci_grace_s for checks to appear at all.
+    ci_wait_s: float = 3600.0
+    ci_grace_s: float = 120.0
 
 
 @dataclass(frozen=True)