feat: audio module, musicgen tests, SQLCipher PRAGMA hardening
#45 — db/base.py: PRAGMA key=? parameterized form instead of f-string
interpolation. Regression tests added (skip when pysqlcipher3 absent).
#50 — circuitforge_core.audio: shared PCM/signal utilities (MIT, numpy-only)
- convert.py: pcm_to_float32, float32_to_pcm, bytes_to_float32
- gate.py: is_silent, rms (RMS energy gate)
- resample.py: resample (scipy.signal.resample_poly; numpy linear fallback)
- buffer.py: ChunkAccumulator (window-based chunk collector + flush)
Replaces hand-rolled equivalents in cf-voice stt.py + context.py.
34 tests, all passing.
#49 — tests/test_musicgen/: 21 tests covering mock backend, factory,
and FastAPI app endpoints. musicgen module was already implemented;
tests were the missing piece to close the issue.