feat: Add GitHub infrastructure, CI/CD pipelines, and examples

- Add GitHub issue templates (bug, feature, docs)
- Add pull request template with closed-source checklist
- Add CODEOWNERS for code review assignment
- Add CI/CD workflows (ci, lint, security, docs, release)
  - pytest + coverage with Python 3.10/3.11 matrix
  - Ruff + MyPy code quality checks
  - Bandit + safety security scanning
  - Sphinx docs + GitHub Pages deployment
  - Automated PyPI releases on tag push
- Add 6 comprehensive examples + Jupyter quickstart
  - 01_factor_discovery.py (LLM factor generation)
  - 02_factor_evolution.py (factor optimization)
  - 03_strategy_generation.py (IC-weighted combination)
  - 04_backtest_simple.py (strategy backtesting)
  - 05_model_training.py (XGBoost/LSTM training)
  - 06_rl_trading_agent.py (PPO/DQN/A2C agents)
  - notebooks/quickstart.ipynb (interactive tutorial)
- Restructure .gitignore with explicit closed-source sections
- Add CI/coverage/license badges to README
- Complete CLI docstrings for all 9 commands
- Add data_config.yaml for quant loop configuration

rdagent/app/cli_welcome.py

@@ -95,3 +95,8 @@ def show_welcome():
 
 if __name__ == "__main__":
     show_welcome()
+
+
+def main():
+    """Entry point for 'predix' CLI command."""
+    show_welcome()