feat: introduce GRPO GPU fallback support, enhance training script with warmstart tagging, and add learning rate parameter for improved training flexibility

feat: introduce reward ablation configurations for enhanced training flexibility, implement YAML loading with extends support, and add reward variant tracking in training scripts

feat: update README with GPU-utilization tuning instructions, enhance modal training script with run name parameter, and modify GRPO configuration for trace logging and vLLM settings

feat: add episode trace fingerprinting for improved trace logging and update reward penalties in GRPO configuration

feat: enhance scenario authoring and caching mechanisms, update action submission terminology, and improve reward configuration for CyberSecurity_OWASP environment

feat: update training configuration and documentation for Modal execution, including new model integration and enhanced tracking utilities

feat: implement core RL training infrastructure, including GRPO training, evaluation utilities, custom environments, and Modal-based execution scripts.