Add Weights & Biases experiment tracking

[Edmon02]

Description

Integrate W&B for comprehensive experiment tracking across all pipeline stages.

Tasks

• Data generation metrics: trajectories/hour, reward distribution, verification pass rates
• Training metrics: loss curves, learning rate schedules, VRAM utilization
• Evaluation metrics: benchmark scores per checkpoint
• Artifact logging: best model checkpoints, trajectory samples
• Hyperparameter sweep support via wandb.sweep
• Dashboard templates for reproducibility

Config

# .env
WANDB_API_KEY=your-key
WANDB_PROJECT=rfa-factory