docs(agent): improve repository guidance [skip ci] (#685)

- Add canonical agent and contributor documentation.

- Modernize issue and pull request templates.

- Skip CI for documentation and issue-template-only changes.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,15 +1,46 @@
-# Proposed Changes
-<!--- Provide a general summary of your changes -->
+## Summary
+
+<!-- Explain the problem and the resulting behavior. Keep implementation details in the sections below. -->
+
+## Changes
 
--
--
 -
 
-## Checklist
+## Related issues
 
-- [ ] Tested locally
-- [ ] Ran `site.yml` playbook
-- [ ] Ran `reset.yml` playbook
-- [ ] Did not add any unnecessary changes
-- [ ] Ran pre-commit install at least once before committing
-- [ ] 🚀
+<!-- Use "Fixes #123" when this pull request should close an issue. Write "None" when not applicable. -->
+
+## Testing
+
+<!-- List exact commands, scenarios, and relevant manual checks. Do not check a box for a test that was not run. -->
+
+- [ ] `pre-commit run --all-files`
+- [ ] Relevant Ansible syntax checks
+- [ ] Relevant focused regression tests
+- [ ] Relevant Molecule scenario
+- [ ] Provisioning tested against a non-production cluster
+- [ ] Reset behavior tested against a non-production cluster
+
+Not run, with reason:
+
+## Risk and compatibility
+
+<!-- Cover existing clusters, upgrades, networking, supported platforms, security, and rollback. Write "None" when a
+category is not affected. -->
+
+- Existing cluster or upgrade impact:
+- Networking or CNI impact:
+- Security impact:
+- Rollback plan:
+
+## Documentation
+
+<!-- Identify updated docs and sample configuration, or explain why no documentation change is needed. -->
+
+## Final checklist
+
+- [ ] The change is focused and contains no unrelated edits.
+- [ ] Tests cover new behavior or a regression, where applicable.
+- [ ] User-facing variables are documented in role defaults, sample inventory, and the README.
+- [ ] Logs, examples, and configuration contain no secrets or identifying infrastructure details.
+- [ ] Generated files and local environment files are not included.