feat(plugin): JUCE-free DSP for all four effect types with Python parity fixtures

Adds plugin/src/dsp (Effect interface, eq, distortion, compressor,
reverb with a direct convolver, factory), parity fixtures rendered by
inference/diagnostics/render_parity_fixtures.py, parity and math tests,
the SEMANTIFX_DSP_ONLY CMake mode, and scripts/check-dsp.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
84080a0d38flamboh committed on 9/19/2026, 5:12:08 AMparent7a0475e
64 files changedLine totals unavailable