feat: add monorepo structure with versioning and CI/CD

Monorepo Features:
- Root package.json with convenient npm scripts for all agents
- Easy testing from root: npm test, npm run test:openagent, npm run test:opencoder
- Multi-model support: test with Grok, Claude, or GPT-4
- Quick dashboard access: npm run dashboard
- No folder navigation required

Versioning System:
- VERSION file tracking current version (0.1.0-alpha.1)
- CHANGELOG.md with comprehensive version history
- Version bump scripts for alpha, beta, rc, and stable releases
- Semantic versioning with progression: Alpha → Beta → RC → Stable

CI/CD:
- GitHub Actions workflow for automated testing
- Pre-merge validation for agent changes
- Smoke tests for both openagent and opencoder
- Automated test result reporting
- Runs on PRs to main/dev and pushes to main

Helper Scripts:
- scripts/test.sh: Advanced test runner with multi-agent support
- scripts/dashboard.sh: Enhanced dashboard launcher with auto-open
- scripts/bump-version.sh: Version management tool

Documentation:
- QUICK_START.md: Comprehensive testing and usage guide
- Clear examples for all test scenarios
- Multi-agent and multi-model workflows

Benefits:
- Easy testing from root directory
- Automated quality checks before merges
- Clear version tracking and history
- Developer-friendly workflows
- No breaking changes to existing structure