docs: add PR-REVIEW.md checklist and link from CONTRIBUTING

Publish the 13-criteria PR review checklist the maintainer runs on
every incoming PR so contributors (and their coding agents) can run
the same pass before opening, surfacing problems before the review
round trip. CONTRIBUTING.md gets a new 'Self-review against the
project review checklist' subsection under 'Submitting pull requests'
and a Further Reading entry. CHANGELOG [Unreleased] gets an Added
entry.

CONTRIBUTING.md

@@ -148,6 +148,20 @@ that touches your code path.
 This is the same matrix that runs on GitHub Actions. Catching a
 regression locally is much cheaper than catching it in CI.
 
+### Self-review against the project review checklist
+
+The 13-criteria checklist the maintainer runs on every incoming PR is
+published at [PR-REVIEW.md](PR-REVIEW.md). Run your own change through
+it before opening — or hand the document to your coding agent with
+"review my branch against this checklist" and let it do the pass. The
+checklist covers PR hygiene (body, commit shape, base freshness), diff
+content (does the change do what the description says, does it fit the
+codebase as a natural extension), and cross-cutting concerns (tests,
+docs, dependencies, security, contributor-conventional Rust patterns).
+
+This is the first thing the maintainer does on any submission, so
+running it yourself saves a review round trip.
+
 ### Additional requirements for feature PRs
 
 - **New CI coverage.** Features added without a test that exercises
@@ -233,6 +247,9 @@ home yet, file a GitHub issue with the `design` label.
 
 ## Further reading
 
+- [PR-REVIEW.md](PR-REVIEW.md) — the 13-criteria PR review checklist
+  the maintainer runs on every incoming PR; run it yourself before
+  opening to save a round trip.
 - [docs/design/README.md](docs/design/README.md) — protocol design tree.
 - [docs/branching.md](docs/branching.md) — full release workflow and
   merge-direction rationale.