Implement consumed episodes management

[omiDBaghi]

Fix: Prevent duplicate score counting by tracking consumed episodes

Adds consumed-episodes directory to track episodes that have already been used for training. Filters out consumed episodes in discover_episode_metadata to prevent the same rewards from being counted multiple times.

Fixes #26

Context

This fix addresses issue #26 where scores were being counted multiple times because episodes were reused across training runs.

Summary of Change

• Added import shutil for file operations
• Added get_consumed_episodes_dir() to determine consumed episodes directory path
• Added mark_episodes_as_consumed() to move used episodes to consumed-episodes directory
• Modified discover_episode_metadata() to filter out already-consumed episodes
• Episodes are now tracked in persistent-data/state-service/consumed-episodes after training

Tests

Tested manually by:

1. Running CodeAssist and earning score
2. Exiting with Ctrl+C
3. Restarting and exiting again with Ctrl+C
4. Verifying that consumed episodes were moved to consumed-episodes directory
5. Confirming that score is not re-counted on subsequent runs

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