M7.3: nisse-review's first slice

A new package over nisse-core: it reviews every ready PR in the
repositories its account can read, and posts one COMMENT review.

- scheduler: each round, open PRs per readable repository (or the
  configured repositories); an item per PR, ready unless draft or WIP;
  closed with the PR. One review at a time, oldest first.
- reader: the repository at head and base from Gitea archives, unpacked
  and read in Python (read_file, list_files, search_code), and its issues;
  bound to the item's repository; no git, no shell.
- review: starts from the PR, commits, diff, comments, closed issues, CI;
  comment drafts a point on any existing line; post_review posts one
  COMMENT review at the head, inline where Gitea takes it, else as links in
  the summary. ask_expert; vault and memory (memory/nisse-review).
- L8: posting is an intent; recovery asks Gitea for the marked review and
  never posts twice; with Gitea down, the item waits.
- Failures retried, then said on the PR until the next push.
- Startup refuses an account that can push to or administer any repo.
- nisse-core gitea: readable_repositories, open_pull_requests, diff,
  commits, archive, issue, search_issues, reviews, post_review; PR fields.
- Bring-up: scripts/review-bringup.sh; nisse-review.example.yaml.
- Tests: unit over a fake Gitea and scripted model; a live test
  (NISSE_REVIEW_GITEA_TOKEN) reviews a PR in a fresh test repository.
- Docs: Development Plan M7.3, Tuning Guide (tuning.review.*).

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

docs/Tuning-Guide.md

@@ -597,3 +597,44 @@ work goes on: SSH comes up before a VM has finished booting.
   services, and fails in confusing ways.
 - **Too high:** work waits after the VM is ready.
 - **Deciding:** how long the template takes from SSH answering to fully up.
+
+## nisse-review's knobs
+
+`nisse-review` (Part R) has its own configuration (`nisse-review.example.yaml`).
+`llm.*`, `tuning.expert.consult_budget` and `tuning.context` mean what they
+mean for `nisse-dev`, above.
+
+### `tuning.review.poll_s` — default 60
+
+How often Gitea is asked for PRs that are ready, when nothing is waiting for a
+review. Each round lists every readable repository's open PRs: a few API calls
+per repository.
+
+- **Too low:** load on Gitea for nothing; reviews don't start much sooner.
+- **Too high:** a PR waits that long for its review to start.
+
+### `tuning.review.max_turns` — default 40
+
+A review run's turn cap. Reading files, searching and drafting comments each
+take a turn; a review that hits the cap posts nothing and counts as a failed
+try.
+
+- **Too low:** large PRs fail to be reviewed.
+- **Too high:** a reviewer that wanders spends long on one PR.
+- **Deciding:** look at how many turns real reviews take (the transcript) and
+  leave headroom.
+
+### `tuning.review.diff_chars` — default 60000
+
+How much of the PR's diff goes into the review's starting context; the rest it
+reads file by file.
+
+- **Too low:** the reviewer reads files it could have seen in the diff.
+- **Too high:** a large diff fills the window before the review starts.
+- **Deciding:** a fraction of the reviewer's context window (about four
+  characters a token).
+
+### `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.