feat: WP-0005 adoption polish — doc sync, fleet parity, CI lint

- Add make agents-sync-package and release-check parity gate
- Add tests/test_packaged_agents_parity.py; sync packaged agents with agents/
- Update install docs (HELLO_WORLD, CLI_CHEAT_SHEET, AGENT_DISTRIBUTION)
- Expand PACKAGE_RELEASE.md secrets setup and pre-tag checklist
- Add flake8 to Gitea CI; CHANGELOG Unreleased for v1.2.0
- Expand INTEGRATION_PATTERNS activity-core handoff checklist

CONTRIBUTING.md

@@ -32,6 +32,12 @@ pip install -e .              # project venv
 pipx install -e . --force     # global pipx install
 ```
 
+**Consumers (pip install from registry):** see [docs/PACKAGE_RELEASE.md](docs/PACKAGE_RELEASE.md)
+for Gitea PyPI credentials and `--extra-index-url` install paths.
+
+**Maintainers (release):** `make agents-sync-package` before tagging when `agents/` changes;
+`make package-check` and the pre-tag checklist in `docs/PACKAGE_RELEASE.md`.
+
 ## Development Workflow
 
 ### Project Structure