Continues the modularization. Moves the four audit handlers
(--validate-zone-pack, --validate-project-packs, --info-zone-deps,
--info-project-deps) into their own file using the same
handle<Family>(int& i, int argc, char** argv, int& outRc) pattern.
Side-cleanup: the two project-scope audits had identical
subprocess-fanout structure (enumerate zones → run per-zone
command → tally PASS/FAIL → print summary). Consolidated that
into a shared runPerZoneAudit helper. Saves ~80 lines of
duplicated dispatch code.
main.cpp drops 28,070 → 27,736 lines (-334). Audit family is
fully self-contained (~330 lines), behavior unchanged
(verified all 4 commands against existing test zones).
