nisse-review: later reviews, replies, rounds, stop and review (M7.5)

Back on a PR it reviewed: a new head gets a later review of the commits
since (each one's diff, through the API) and of its earlier points; what
was said since gets replies, answered where it was said or skipped with a
reason. It signs off once and stays quiet while still happy. Past
tuning.review.max_rounds it sums up for the operator and goes quiet,
until a push or someone other than the PR's author joins in. An
operator's `stop` quiets it; `review` asks for a fresh review.

Reviews carry numbered markers and replies their point's key, so
recovery posts nothing twice.

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

docs/Tuning-Guide.md

@@ -637,7 +637,8 @@ reads file by file.
 ### `tuning.review.attempts` — default 2
 
 Failed review runs on one PR, at one head, before the reviewer says on the PR
-that it couldn't review it, and stops trying until the next push.
+that it couldn't review it, and stops trying until the next push or an
+operator's `review` comment.
 
 ### `tuning.review.ci_wait_s` — default 3600
 
@@ -661,3 +662,17 @@ review test, whose fresh repository has no CI).
 
 - **Too low:** a review starts before CI has reported, and runs beside it.
 - **Too high:** repositories without CI wait that long for every review.
+
+### `tuning.review.max_rounds` — default 4
+
+Rounds of discussion on one PR before the reviewer stops answering (R2): a
+round is a review it posts, or a run in which it replied. Past the cap, it
+posts one summary of what is still open, for the operator, and goes quiet
+on that PR. A new push, or a comment from anyone but the reviewer and the
+PR's author, starts the count again.
+
+- **Too low:** a disagreement worth one more exchange goes to the operator.
+- **Too high:** two agents argue at length (and GPU time) before anyone looks.
+- **Deciding:** a review, the author's answers, its replies, and one more
+  exchange is four; raise it if summaries arrive while the two are still
+  converging.