chore: add PR automation workflows for triage, formatting, staleness, and overlap detection (#263)

AGENTS.md

@@ -28,10 +28,10 @@ This is a pre-release project. Do not add backwards compatibility or legacy patt
 
 Read [CONTRIBUTING.md](CONTRIBUTING.md) before opening a PR. Key rules:
 
+- **You MUST use the PR template.** Every PR must include the PR template with all sections filled out. The template is loaded automatically when you create a PR via the GitHub UI. If you create a PR via the API or CLI, copy the template from `.github/PULL_REQUEST_TEMPLATE.md` into the PR body. **PRs that do not use the template will be closed automatically by CI.**
 - **Features require a prior approved Discussion.** Do not open a feature PR without one. It will be closed. Open a [Discussion](https://github.com/emdash-cms/emdash/discussions/categories/ideas) in the Ideas category first.
 - **Bug fixes and docs** can be PRed directly.
-- **Fill out the PR template completely.** Every section. Check every applicable checkbox. PRs with empty or skipped templates will be closed.
-- **Check the AI disclosure box** in the PR template if any part of the code was AI-generated.
+- **Check every applicable checkbox** in the PR template, including the "I have read CONTRIBUTING.md" box and the AI disclosure box if any part of the code was AI-generated.
 - **Do not make bulk/spray changes** (e.g., "fix all lint warnings", "add types everywhere", "improve error handling across codebase"). If you see a systemic issue, open a Discussion.
 - **Do not touch code outside the scope of your change.** No drive-by refactors, no "while I'm here" improvements, no added comments or logging in unrelated files.
 - **All CI checks must pass.** Typecheck, lint, format, and tests. No exceptions.