feat: US-008 - Add CONTRIBUTING.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CONTRIBUTING.md

@@ -0,0 +1,43 @@
+# Contributing to Agent Loop
+
+Thanks for your interest in contributing!
+
+## Running Locally
+
+```bash
+git clone https://github.com/sheldonchiu/agent-loop.git
+cd agent-loop
+./install.sh
+```
+
+This copies the harness to `~/.claude/loop/` and installs slash commands.
+
+## Testing Changes
+
+Use `--dry-run` to verify your changes without executing Claude Code sessions:
+
+```bash
+.loop/loop.sh --dry-run
+```
+
+This prints the assembled prompts so you can inspect generator and evaluator
+behavior without running actual iterations.
+
+For shell script changes, validate syntax:
+
+```bash
+bash -n loop.sh
+bash -n lib/*.sh
+```
+
+## Submitting a Pull Request
+
+1. Fork the repository and create a feature branch
+2. Make your changes — keep commits focused and small
+3. Test with `--dry-run` and `bash -n` as described above
+4. Open a PR against `main` with a clear description of what and why
+5. One approval required before merge
+
+## Questions?
+
+Open an issue — we're happy to help.