feat(relay): add a CAS publication receipt for closed reviewed revisions

skills/relay/references/plain-git-publication.md

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+# Plain Git publication
+
+Publish an already closed Reviewed Result to a plain Git remote. This is not
+review, recovery, Change Request creation, or Landing.
+
+```bash
+node "${RELAY_SKILL_ROOT:-skills}/relay/scripts/publish-reviewed-revision.js" \
+  --run-dir "$RUN_DIR" \
+  --remote "$REMOTE_URL" \
+  --ref refs/heads/published \
+  --expected-old "$EXPECTED_OLD_OID" \
+  --json
+```
+
+The immutable input is the terminal `reviewed_result_ready` close plus its
+bound passing review and verification. The push uses a compare-and-swap
+`--force-with-lease=<ref>:<expected-old-oid>` update and confirms success with
+`git ls-remote`. Retries are idempotent: an already-published OID converges to
+`already_published`; concurrent destination movement fails closed without
+`--force`. The receipt records remote URL identity, destination ref, expected
+old OID, published OID, and the post-push observation. No run fact is appended.