main.cpp had grown past 28k lines, with each new procedural-
generation command adding 100-200 lines to the inline if/else
dispatch chain. This commit starts breaking that up by moving
the four audio-related handlers (--gen-audio-tone, -noise,
-sweep, --gen-zone-audio-pack) into their own translation unit.
Pattern established here for future family extractions:
- Family lives in cli_<family>.{hpp,cpp}
- Single dispatch entry point: bool handle<Family>(int& i, int argc,
char** argv, int& outRc) — true if matched (writes outRc), false
to fall through.
- main.cpp's argv loop calls each family's dispatcher first and
returns its outRc on match, before the legacy in-line chain.
Side-benefit: consolidated the duplicated 25-line WAV header
writer + 5ms attack/release envelope into shared helpers
(writeWavMono16, applyEdgeEnvelope) at the top of the new file.
main.cpp drops from 28,943 → 28,329 lines (-614). Audio family
is fully self-contained (~440 lines), behavior unchanged
(verified by re-running tone/noise/sweep + zone-audio-pack).
