fix: resolve 500 error on /schema and add extra validation tasks

fix: standardize grader structure to tasks/ directory for OpenEnv validation compliance

fix: add mandatory /metadata and /schema endpoints for OpenEnv validation and update task metadata

Fix OpenEnv task mapping schema: Add required 'id' fields

Fix OpenEnv validation: Use explicit python grader for tasks

fix: task routing by name, remove out-of-range rewards, add grader field to tasks

fix: strictly bound task scores to satisfy OpenEnv Phase 2 testing bounds

feat: add inference.py, openenv.yaml, bug dataset & openai dep for hackathon submission