Moves the two cleanup-pass handlers (--strip-zone,
--strip-project) out of main.cpp into a new
cli_strip.{hpp,cpp} module. Both remove derived outputs
(.glb / .obj / .stl / .html / .dot / .csv / .png /
ZONE.md / DEPS.md) leaving only source files. Useful before
--pack-wcp so archives don't carry redundant exports, and
before committing to git so derived blobs don't bloat
history. Both honor --dry-run for safe previews.
main.cpp shrinks by 164 lines (4,110 to 3,946).
