chore(governance): add release-kit overlay + PR self-check + auto-release workflow (#35)

Implements cc-rules v1.4's 第五律 5.5 project overlay requirement.

- CLAUDE.md: declare release_kit: YAML block (version_source,
  changelog, release_channel, docs_source, resource_lists,
  new_feature_doc_expectations, bootstrap_quirk_policy)
- .github/PULL_REQUEST_TEMPLATE.md: add 5.3 user-visible-change
  self-check section with reviewer gate instruction
- .github/workflows/release.yml (NEW): auto-create GitHub Release
  from CHANGELOG.md section on v* tag push. Idempotent (checks if
  release already exists). Closes the gap that caused v3.9.0 /
  v3.10.0 / v3.11.0 to each miss their GH Release.

Governance-only change. No code, no user-visible behavior change
(the workflow only fires on future tags). No README update needed.

Co-authored-by: Tao Deng <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -38,3 +38,10 @@ Reviewers: this section is for you, not the author. Do not approve until every b
 - `ALIGNMENT.md` Rule(s) invoked: <!-- e.g. Rule 3 -->
 - Related issue / prior PR: <!-- #NNN -->
 - Historical lesson reference (if relevant): <!-- e.g. 2026-04-11 drift, b87992f -->
+
+### User-visible change self-check (铁律第五律 5.3)
+
+- [ ] This PR has user-visible changes → README has corresponding documentation (paste diff link or line range)
+- [ ] This PR has no user-visible changes → stated "no user-visible change" in summary above
+
+Reviewers: if "user-visible" is checked but README diff is empty, block merge (per 5.3 reviewer gate).