Add CONTRIBUTING.md (#24)

Author: benvinegar

CONTRIBUTING.md

@@ -0,0 +1,61 @@
+# Contributing to Baudbot
+
+## Setup
+
+```bash
+git clone https://github.com/modem-dev/baudbot.git ~/baudbot
+npm install
+```
+
+## Running Tests
+
+```bash
+# All tests (207 across 5 suites)
+bin/test.sh
+
+# JS/TS only
+bin/test.sh js
+
+# Shell only
+bin/test.sh shell
+
+# Lint + typecheck
+npm run lint && npm run typecheck
+```
+
+## Branches and PRs
+
+- Don't commit directly to `main`. Open a PR from a feature branch.
+- Branch names: `<your-gh-username>/<description>` (e.g. `benvinegar/fix-firewall-rules`)
+- Commit messages: prefix with area. Examples: `security: add rate limiting`, `bridge: fix reconnect`, `docs: update README`
+- One branch per change. Keep PRs focused.
+
+## Code Conventions
+
+- Scripts must work on both Ubuntu and Arch Linux. Use POSIX tools, `grep -E` (not `grep -P`), and avoid distro-specific package manager calls.
+- Security functions must be pure, testable modules with no side effects or env vars at module scope.
+- All security code needs tests before merging.
+- New integrations get their own subdirectory (e.g. `discord-bridge/`).
+
+## Security Changes
+
+If your change touches security code (`tool-guard.ts`, `security.mjs`, firewall scripts, etc.):
+
+1. Add or update tests.
+2. Run `bin/security-audit.sh --deep` and confirm it passes.
+3. Note the security implications in your PR description.
+
+See [SECURITY.md](SECURITY.md) for the threat model and architecture.
+
+## Reporting Bugs
+
+Open a GitHub issue. Include:
+
+- What you did
+- What you expected
+- What happened instead
+- OS and version (Ubuntu/Arch/other)
+
+## Security Vulnerabilities
+
+Do **not** open a public issue for security vulnerabilities. See [SECURITY.md](SECURITY.md) for reporting instructions.