feat(editor): --info-wob-stats + fix weld hash collision bug

Add --info-wob-stats reporting per-group + aggregate
triangle counts, surface area, edge analysis, and watertight
check for WOB buildings. Same flag surface as --info-mesh-stats
including --weld <eps> for true topological closure check
on per-face-vertex meshes.

Also fixes a correctness bug in the weld implementation
of --info-mesh-stats: the previous code used a 64-bit hash
of the quantized position as the equality key, which gave
false-positive collisions that incorrectly merged distinct
vertices. A unit cube's 8 corners collapsed to 2 positions
under the buggy hash. Replace with std::map keyed on the
actual quantized (qx, qy, qz) tuple so equality is exact.

Re-verified: cube 8→8 watertight YES; firepit 240→80
watertight YES (was wrongly reporting 56 unique with 48
non-manifold edges); tent_solid 18→6 watertight YES;
tent_fixed 21→9 with 5 boundary edges at the door perimeter
(correct — door is intentionally open).

tools/editor/cli_arg_required.cpp

@@ -14,7 +14,7 @@ const char* const kArgRequired[] = {
     "--info-zone-models-total", "--info-project-models-total",
     "--list-zone-meshes-detail", "--list-project-meshes-detail", "--info-mesh",
     "--info-mesh-storage-budget", "--info-mesh-stats",
-    "--info-wob", "--info-woc", "--info-wot",
+    "--info-wob", "--info-wob-stats", "--info-woc", "--info-wot",
     "--info-creatures", "--info-objects", "--info-quests",
     "--info-extract", "--info-extract-tree", "--info-extract-budget",
     "--list-missing-sidecars",