Moves the two spatial-bounds info handlers (--info-zone-extents,
--info-project-extents) out of main.cpp into a new
cli_info_extents.{hpp,cpp} module. Both compute world-space XYZ
bounding boxes from manifest tile coords + per-chunk height
samples; the project variant unions every zone's box into one.
main.cpp shrinks by 232 lines (7,695 to 7,463). Both --json
output modes preserved for camera-framing pipelines.
