Add PR template, issue templates, and contribution policy (#126)

* chore: add PR template, issue templates, and contribution policy

Drive-by feature PRs are becoming a problem. This adds guardrails:

- PR template with type selection, checklist, and AI disclosure
- Bug report issue template (structured YAML form)
- Issue config that redirects features to Discussions and disables blank issues
- PR compliance workflow that enforces template completion and requires
  a Discussion link for feature PRs
- Contribution policy in CONTRIBUTING.md (acceptance tiers, AI PR rules)
- Agent-facing rules in AGENTS.md (follow the template, no bulk changes)

* fornat

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,37 @@
+## What does this PR do?
+
+<!-- Describe the change and why it's needed. Link to a related issue or discussion. -->
+
+Closes #
+
+## Type of change
+
+<!-- Check one. If "Feature", a prior Discussion is required — see below. -->
+
+- [ ] Bug fix
+- [ ] Feature (requires [approved Discussion](https://github.com/emdash-cms/emdash/discussions/categories/ideas))
+- [ ] Refactor (no behavior change)
+- [ ] Documentation
+- [ ] Performance improvement
+- [ ] Tests
+- [ ] Chore (dependencies, CI, tooling)
+
+## Checklist
+
+- [ ] I have read [CONTRIBUTING.md](https://github.com/emdash-cms/emdash/blob/main/CONTRIBUTING.md)
+- [ ] `pnpm typecheck` passes
+- [ ] `pnpm --silent lint:json | jq '.diagnostics | length'` returns 0
+- [ ] `pnpm test` passes (or targeted tests for my change)
+- [ ] `pnpm format` has been run
+- [ ] I have added/updated tests for my changes (if applicable)
+- [ ] New features link to an approved Discussion: https://github.com/emdash-cms/emdash/discussions/...
+
+## AI-generated code disclosure
+
+<!-- If any part of this PR was generated by AI tools (Copilot, Claude, GPT, Cursor, etc.), check the box. This is fine — we just need to know so reviewers can pay extra attention to edge cases. -->
+
+- [ ] This PR includes AI-generated code
+
+## Screenshots / test output
+
+<!-- Optional. Include if the change is visual or if you want to show test results. -->