Three callers were each open-coding the same quantize-and-
bucket pass over vertex positions: --info-mesh-stats,
--info-wob-stats, and --bake-wom-collision. Move the
implementation to cli_weld.{hpp,cpp} as buildWeldMap() and
have each caller pass a flat positions array.
Identical std::map-based exact-equality keying preserved
(unbalanced-hash collisions remain absent). All three call
sites verified to produce byte-identical output:
• info-mesh-stats firepit: 240→80 verts, 0 boundary
• info-wob-stats cube: 8→8 verts, watertight YES
• bake-wom-collision tent: 18→6 verts, 8-tri WOC
About 75 lines of duplication removed; future weld-using
commands now opt in by including one header.
