docs: Add GitHub Copilot instructions

.github/copilot-instructions.md

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+# ESLint GitHub Bot
+
+ESLint GitHub Bot is a Probot-based GitHub application that automates common tasks for repositories managed by the ESLint team. The bot handles commit message validation, work-in-progress PR management, automatic issue assignment, release monitoring, recurring issue creation, and needs-info processing.
+
+Always reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here.
+
+## Working Effectively
+
+### Bootstrap and Setup
+- Clone the repository
+- `npm install` -- takes 1-30 seconds depending on npm cache state. Works with Node.js 20.x but shows engine warnings (expects Node.js 22.x)
+- Create `.env` file for local development:
+  ```bash
+  echo 'APP_ID=12345
+  PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----
+  [valid PEM private key content]
+  -----END RSA PRIVATE KEY-----"
+  WEBHOOK_SECRET=test_webhook_secret_123
+  PORT=3000' > .env
+  ```
+
+### Build and Test
+- `npm run lint` -- takes ~1.5 seconds. NEVER CANCEL. Uses ESLint with eslint-config-eslint
+- `npm test` -- takes ~3 seconds. NEVER CANCEL. Runs Jest with 284 tests achieving 98.31% coverage
+- Run the web server: `npm start` -- starts immediately on port 3000
+- Health check: `curl http://localhost:3000/ping` returns "PONG" in ~1.6ms
+
+### Environment Requirements
+- Node.js 22.x preferred (works on 20.x with warnings)
+- npm 10.x
+- Environment variables for server operation:
+  - `APP_ID`: GitHub app ID (can be dummy value like 12345 for local testing)
+  - `PRIVATE_KEY`: Valid PEM private key (required format, can be test key for local development)
+  - `WEBHOOK_SECRET`: Webhook secret (can be dummy value for local testing)
+  - `PORT`: Server port (optional, defaults to 3000)
+
+## Validation
+
+### Manual Testing Requirements
+- ALWAYS run the full test suite after making changes: `npm test`
+- ALWAYS run linting before committing: `npm run lint`
+- Test server startup: `npm start` and verify health check responds: `curl http://localhost:3000/ping`
+- For plugin changes, run relevant test files: `npm test tests/plugins/[plugin-name]/index.js`
+
+### Critical Timing Requirements
+- **NEVER CANCEL** any commands - all operations complete quickly
+- npm install: 1-30 seconds (set timeout to 60+ seconds)
+- npm test: ~3 seconds (set timeout to 30+ seconds)
+- npm run lint: ~1.5 seconds (set timeout to 30+ seconds)
+- Server startup: immediate (set timeout to 10+ seconds)
+
+## Common Tasks
+
+### Plugin Development
+The bot uses a plugin architecture with 6 core plugins in `src/plugins/`:
+
+1. **auto-assign** (`src/plugins/auto-assign/index.js`): Auto-assigns issues to users who indicate willingness to submit PRs
+2. **commit-message** (`src/plugins/commit-message/index.js`): Validates PR titles follow ESLint commit message guidelines
+3. **needs-info** (`src/plugins/needs-info/index.js`): Adds comments when "needs info" label is added to issues
+4. **recurring-issues** (`src/plugins/recurring-issues/index.js`): Creates new scheduled release and TSC meeting issues
+5. **release-monitor** (`src/plugins/release-monitor/index.js`): Manages PR status during release phases
+6. **wip** (`src/plugins/wip/index.js`): Handles work-in-progress PR status based on title/labels
+
+### Adding New Plugins
+1. Create plugin file in `src/plugins/[plugin-name]/index.js`
+2. Add plugin to exports in `src/plugins/index.js`
+3. Add plugin to enabled list in `src/app.js`
+4. Create tests in `tests/plugins/[plugin-name]/index.js`
+5. Follow existing plugin patterns using Probot event handlers
+
+### File Structure Reference
+```
+src/
+├── app.js                 # Main application entry point
+├── constants.js           # Shared constants (currently empty)
+└── plugins/
+    ├── index.js          # Plugin exports
+    ├── auto-assign/
+    ├── commit-message/
+    ├── needs-info/
+    ├── recurring-issues/
+    ├── release-monitor/
+    └── wip/
+
+tests/
+├── __mocks__/            # Test mocks
+└── plugins/              # Plugin tests mirror src structure
+
+.github/
+└── workflows/
+    ├── ci.yml           # CI pipeline (lint + test)
+    ├── deploy.yml       # Deployment workflow
+    ├── add-to-triage.yml
+    └── stale.yml
+
+docs/
+├── commit-message-check.md  # Commit message validation docs
+└── edit-pr-title-explanation.png
+```
+
+### Key Configuration Files
+- `package.json`: Dependencies, scripts, Jest config
+- `eslint.config.js`: ESLint configuration using eslint-config-eslint
+- `.editorconfig`: Code formatting rules
+- `Procfile`: Production deployment config for Dokku
+- `.gitignore`: Excludes node_modules, coverage, .env, *.pem files
+
+### Common Command Outputs
+
+#### Repository Root Files
+```bash
+$ ls -la
+.editorconfig
+.git/
+.github/
+.gitignore
+.npmrc
+CONTRIBUTING.md
+LICENSE
+Procfile
+README.md
+docs/
+eslint.config.js
+package-lock.json
+package.json
+src/
+tests/
+```
+
+#### Package.json Scripts
+```json
+{
+  "scripts": {
+    "lint": "eslint .",
+    "lint:fix": "npm run lint -- --fix", 
+    "start": "node ./src/app.js",
+    "test": "jest --colors --verbose --coverage"
+  }
+}
+```
+
+#### Test Coverage Summary
+```
+All files                 |   98.31 |     93.1 |   98.36 |   98.21 |
+Test Suites: 6 passed, 6 total
+Tests:       284 passed, 284 total
+Time:        ~3 seconds
+```
+
+## Troubleshooting
+
+### Node.js Version Warnings
+- Repository expects Node.js 22.x but works on 20.x with warnings
+- Engine warnings are normal and do not prevent functionality
+- All commands and tests work correctly despite version mismatch
+
+### Server Won't Start
+- Ensure `.env` file exists with required environment variables
+- `PRIVATE_KEY` must be valid PEM format (can be test key for local development)
+- Server defaults to port 3000, check for port conflicts
+
+### Test Failures
+- Run `npm install` to ensure dependencies are current
+- Check that changes don't break existing plugin functionality
+- Verify new tests follow existing patterns in `tests/plugins/` structure
+
+### Deployment Notes
+- Production deployment uses Dokku to github-bot.eslint.org
+- Health check endpoint: https://github-bot.eslint.org/ping
+- Webhook URL: /api/github/webhooks (Probot default)
+- Uses `Procfile` for production process management
+
+## Development Workflow
+
+1. Make changes to plugin code in `src/plugins/`
+2. Update or add tests in `tests/plugins/`
+3. Run `npm test` to verify all tests pass (NEVER CANCEL - takes ~3 seconds)
+4. Run `npm run lint` to check code style (NEVER CANCEL - takes ~1.5 seconds)
+5. Test server functionality: `npm start` and verify `/ping` responds
+6. For plugin changes, manually test relevant GitHub webhook scenarios if possible
+
+Always follow this complete validation workflow before committing changes.