feat(editor): add --bake-wob-collision multi-group WOB→WOC

Sibling of --bake-wom-collision for buildings. Walks every
group in a WOB, optionally welds vertices PER GROUP (groups
are intentionally separate — rooms with portals between them,
so welding across groups would fuse walls that should remain
distinct collision surfaces), and appends each to a single
WoweeCollision via WoweeCollisionBuilder::addMesh.

Same flag surface as the WOM variant: optional [out.woc]
output path, --weld <eps> for per-group vertex merge,
--steep <deg> for the walkable/steep slope cutoff.

Smoke tested on a 1-group cube WOB: 8 verts → 12-triangle
WOC with proper bounds (-1,-1,-1)..(1,1,1) and walkable/
steep classification matching the cube face orientations.

tools/editor/cli_arg_required.cpp

@@ -139,7 +139,7 @@ const char* const kArgRequired[] = {
     "--export-stl", "--import-stl",
     "--bake-zone-glb", "--bake-zone-stl", "--bake-zone-obj",
     "--bake-project-obj", "--bake-project-stl", "--bake-project-glb",
-    "--bake-wom-collision",
+    "--bake-wom-collision", "--bake-wob-collision",
     "--audit-watertight",
     "--convert-m2", "--convert-m2-batch",
     "--convert-wmo", "--convert-wmo-batch",