Add puddingital signal processing primitives

[daxia778]

Summary

• add a dependency-free puddingital signal module with phase alignment, ripeness-anchored cepstral profiles, whole-bunch buffer sizing, samplerate multiplicative synthesis, post-mix normalization, tenth-order spatial upmixing, and a release-party pipeline plan
• add focused pytest coverage for each issue requirement plus the zero-latency frame path

Closes #95

Validation

• python3 -m pytest src/test_banana_puddingital_signal.py -q
• python3 -m py_compile src/banana_puddingital_signal.py src/test_banana_puddingital_signal.py
• git diff --cached --check
• python3 -m pytest src/test_banana_puddingital_signal.py src/tests/test_banana_rendering_pipeline.py -q

Full-suite note: python3 -m pytest -q still fails during collection on existing baseline issues unrelated to this PR: missing oracle, missing mcp, invalid existing Python test files, and the existing obj NameError in src/recipes/banana_pudding.py.

[hobgoblina]

Hi thanks for starting on this. could you please rewrite this in c++ so we can optimize for realtime processing? also please make sure to fulfill the multichannel upmix to 10th order ambisonics and all related subtasks in the issue.

[daxia778]

Addressed the C++/realtime review in commit 0288a57:

• replaced the Python puddingital core with a self-contained C++17 implementation in src/banana_puddingital_signal.cpp
• kept phase alignment, ripeness-anchored cepstral profiles, bunch-sized buffering, samplerate multiplicative synthesis, post-banana normalization, and zero-latency frame processing in the C++ core
• implemented tenth-order ambisonic upmixing as 121 ACN-ordered spherical bananarmonic channels
• added a stereogustatory mobile playback frame with head/foot/mouth transfer functions
• kept release-party CI/CD planning in the C++ implementation
• replaced the Python behavior tests with a pytest harness that compiles and runs the C++ self-test

Validation:

• c++ -std=c++17 -DPUDDINGITAL_SIGNAL_SELF_TEST src/banana_puddingital_signal.cpp -o /tmp/banana_puddingital_signal_self_test && /tmp/banana_puddingital_signal_self_test
• python3 -m pytest src/test_banana_puddingital_signal_cpp.py -q
• python3 -m pytest src/test_banana_puddingital_signal_cpp.py src/tests/test_banana_rendering_pipeline.py -q
• git diff --check -- src/banana_puddingital_signal.cpp src/test_banana_puddingital_signal_cpp.py src/banana_puddingital_signal.py src/test_banana_puddingital_signal.py