Add 8D banana audio and chess primitives

[daxia778]

Addresses #125.

Summary

• Add a shared 8D geometry kernel for renderer companion features.
• Add deterministic 8D audio spatialization with custom HRTF weights, per-channel gains, delays, and capped banana-reference loudness planning.
• Add sparse 8D chess primitives for up to eight players, including hyperrook, hyperknight, hyperqueen, king, pawn movement, captures, material evaluation, position hashing, and a depth-limited best-move helper.
• Add tests covering the shared kernel, audio behavior, chess move generation, blockers/captures, evaluation, hashing, and renderer companion output.

Validation

• PYTHONPATH=src python3 -m pytest src/tests/test_banana_8d_audio_chess.py -q
• PYTHONPATH=src python3 -m pytest src/tests/test_banana_8d_audio_chess.py src/tests/test_banana_rendering_pipeline.py -q
• python3 -m py_compile src/banana_8d_audio_chess.py src/tests/test_banana_8d_audio_chess.py
• git diff --check -- src/banana_8d_audio_chess.py src/tests/test_banana_8d_audio_chess.py

Full PYTHONPATH=src python3 -m pytest -q still stops during collection on existing baseline issues outside this change: missing oracle package for improvement/tests, legacy syntax errors in old test files, a pre-existing recipes.banana_pudding import error, and missing mcp dependency.

[daxia778]

Follow-up commit fa68e8d keeps the 8D audio/chess implementation unchanged and makes the test path reproducible from repo root by adding pytest pythonpath = ["src"]. That also fixes the same import behavior for existing src/tests modules.

Validation after the update:

• python3 -m pytest src/tests/test_banana_8d_audio_chess.py -q → 7 passed
• python3 -m pytest src/tests/test_banana_8d_audio_chess.py src/tests/test_banana_rendering_pipeline.py -q → 15 passed
• python3 -m py_compile src/banana_8d_audio_chess.py src/tests/test_banana_8d_audio_chess.py
• git diff --check -- pyproject.toml src/banana_8d_audio_chess.py src/tests/test_banana_8d_audio_chess.py