Add Sanguo Wuxing math model and validation

[naijuan]

What changed

• Add a 7x7 cluster-based Sanguo Wuxing game with base and bonus modes, free-spin progression, feature events, reel generators, and a 50,000x cap.
• Add stream-based Book output support in src/state/state.py to reduce worker memory from shard-sized storage to single-Book storage.
• Add deterministic regression utilities, event-contract validation, reel metadata, and 100k/1m validation snapshots.
• Add M1-M2d delivery notes and project tests.

Why

The game needs a reproducible Stake Engine implementation and validation evidence while avoiding the memory cost of retaining a full worker shard before compression.

Validation

• env/bin/python -m compileall completed successfully.
• env/bin/pytest -q tests/test_sanguo_wuxing.py: 17 passed.
• High-confidence credential scan found no added keys or tokens.
• Generated reel CSV line endings are preserved because their exact bytes are covered by SHA-256 snapshots.

Risk and current status

• This is an M2d development candidate, not a certified math package.
• Base-mode 1m-spin confidence remains wide and both modes require at least 10m follow-up regression before the next gate.
• No 50,000x cap sample was observed in the current million-spin runs.
• The shared state streaming change affects output generation and should receive focused upstream review.

Rollback

Revert this commit to remove the game and restore the previous in-memory Book behavior.