refactor: restructure AGENTS.md with progressive disclosure

Amp-Thread-ID: https://ampcode.com/threads/T-019bdfa7-58b4-731b-83ee-83f2b2bea030
Co-authored-by: Amp <amp@ampcode.com>

docs/guidance/git-workflow.md

@@ -0,0 +1,31 @@
+---
+globs:
+  - '.github/**/*'
+---
+
+# Git & PR Workflow
+
+## Commit Messages
+
+Use `prefix:` format: `feat:`, `fix:`, `test:`, `refactor:`, `docs:`
+
+Never mention Claude/AI in commits.
+
+## Pull Requests
+
+- Reference linked issues: `Fixes #123`
+- Keep descriptions concise and information-dense
+- No emojis or excessive headers
+- Follow the template in `.github/`
+- Keep PRs focused — suggest splitting if >300 lines of non-test code
+
+## Quality Gates (CI)
+
+All must pass before merge:
+
+- `pnpm lint`
+- `pnpm typecheck`
+- `pnpm knip`
+- Relevant tests
+
+Never use `--no-verify` to bypass failing tests. If tests fail, identify root cause and fix or document blockers.