Continues the modularization. Moves the four per-zone inventory
handlers into their own file:
--list-zone-meshes (WOM stats)
--list-zone-audio (WAV header parse)
--list-zone-textures (texture-ref histogram)
--info-zone-summary (BOOTSTRAPPED/PARTIAL/EMPTY status)
Each consumes a trailing --json flag the same way; consolidated
that check into a consumeJsonFlag helper at the top.
main.cpp drops 27,445 → 27,200 lines (-245). Per-zone inventory
behavior unchanged (re-verified all 4 commands).
A pre-existing duplicate --list-zone-meshes handler (the older
detailed per-mesh listing, similar to the --list-project-meshes
collision fixed in 976549fe) is now dead code in the in-line
chain since the extracted module dispatches first. Will rename
or remove that duplicate in a follow-up cleanup.
