Major enhancements: Statistical testing (scipy.stats), large-scale tasks (20/25 stops), OR-Tools/MPC baselines, README visualizations, score range fix (0.01-0.99)

Fix OpenEnv grader detection - Add __all__ exports to tasks.py and grader.py

fix: expand task suite to 5 tasks for maximum validation redundancy

fix: restore legacy map for task_11 and task_21 to prevent Gradio browser cache errors

fix: clean unused imports and adopt strict bot format

fix: refactor to 3 explicit static tasks to guarantee validator discovery

fix: restore backward compatibility for app.py task lookup

feat: expand task suite to 30 tasks with graders for Phase 2 compliance

feat: Dueling DDQN + PER, GTFS demand profiles, convergence analytics, premium UI

feat: complete premium hackathon upgrades with DDQN, XAI, and Compare Mode