Moves the four random-population handlers (--random-populate-zone,
--random-populate-items, --gen-random-zone, --gen-random-project)
out of main.cpp into a new cli_random.{hpp,cpp} module. All four
use the same seeded LCG so re-runs reproduce the same content;
the gen-random-* pair shells out to scaffold-zone +
random-populate-zone + random-populate-items so the simpler
single-purpose handlers stay the source of truth.
main.cpp shrinks by 439 lines (5,788 to 5,349). The inline word
lexicons (creature names, object paths, item prefixes/nouns) move
with random-populate-zone and -items into the new module.
