Moves the two audio-config audit handlers (--info-zone-audio,
--info-project-audio) out of main.cpp into a new
cli_info_audio.{hpp,cpp} module. Both surface the music /
day-ambience / night-ambience / volume settings stored in
zone.json so designers can spot zones still missing audio
assignment before a release pass.
main.cpp shrinks by 127 lines (7,053 to 6,926). Drops the
dead `label` lambda inside info-project-audio that the
unused-but-set-variable warning had been flagging. Both
--json output modes preserved.
