chore: add CLAUDE.md for AI-assisted development (#150)

Author: VincentBee

CLAUDE.md

@@ -0,0 +1,53 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+GitHub Actions Mobsuccess is a GitHub Action that enforces Mobsuccess compliance policies in repositories. It validates pull request titles, branch names, and other repository standards during CI/CD workflows.
+
+## Commands
+
+```bash
+npm ci                # Install dependencies
+npm run eslint        # Lint JavaScript code
+npm run prettier      # Check code formatting
+npm run test          # Run tests with coverage (Jest)
+```
+
+## Architecture
+
+**Entry Point Flow**: `index.js` → `action.js` (dispatcher) → specific action handler in `lib/actions/`
+
+**Three Main Actions**:
+
+- `validate-pr`: Validates branch names and PR titles against conventions
+- `after-pr-merged`: Post-merge automation (rebase notifications for sub-branches)
+- `changelog`: Generates changelog from releases and PRs
+
+**Key Modules**:
+
+- `lib/branch.js`: Branch naming convention validator (regex-based)
+- `lib/pullRequest.js`: PR title validation (Conventional Commits format)
+- `lib/actions/pullRequest.js`: Full PR validation logic including GitHub API calls
+- `lib/actions/octokit.js`: GitHub API client wrapper
+
+## Conventions
+
+**Branch Naming**: `{type}/{name}` where type is one of: `feat|fix|hotfix|chore|docs|refactor|test|revert|ci|perf|style|build|change|remove|poc|mobsuccessbot|dependabot`
+
+Special prefixes: `renovate/`, `copilot/`, `claude/`, `crowdin/update-translations`
+
+**Sub-branches**: Branches based on non-main branches must use `baseRef--` prefix (e.g., `develop--feat/something`)
+
+**PR Titles**: Conventional Commits format: `{type}({scope})!: {description}`
+
+- Types: `hotfix|feat|fix|chore|docs|refactor|test|revert|build|ci|perf|style|change|remove|poc`
+- Scope and `!` (breaking change marker) are optional
+- Revert format: `revert {original message}`
+
+## Testing
+
+Tests use Jest with parametrized test cases (`test.each()`). Run `npm run test` for coverage report.
+
+Test files mirror source files: `lib/branch.test.js`, `lib/pullRequest.test.js`