feat(editor): add --gen-mesh-outhouse small-shed primitive

68th procedural mesh primitive. Built from 3 axis-aligned
boxes:

  • solid body slab spanning width × depth × (height-roofT)
  • thin door slab on the +Z face (pushed slightly outward
    so it visually sits on the wall — gives doorframe-like
    relief without a real cutout)
  • roof slab slightly larger than the body footprint and
    sitting on top, controlled by roofOverhang

Distinct from --gen-mesh-house (multi-walled, peaked-roof
dwelling). An outhouse is the single-room privy / tool shed
variant — useful for villages, frontier outposts, small
farms, refuse-shed corners.

Watertight under weld (verified 54 manifold edges, 0
boundary, 0 non-manifold). First handler to use the new
setCenteredBoundsXZ helper from this batch.

tools/editor/cli_help.cpp

@@ -260,6 +260,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Training dummy: post + cubic torso + cross-bar arms + optional head (sparring / drill yard)\n");
     std::printf("  --gen-mesh-hitching-post <wom-base> [span] [height] [postW] [barT] [capH]\n");
     std::printf("                         Hitching post: 2 vertical posts + horizontal cross-bar + optional decorative caps (stable / town square)\n");
+    std::printf("  --gen-mesh-outhouse <wom-base> [width] [depth] [height] [doorH] [doorW] [roofOverhang] [roofT]\n");
+    std::printf("                         Outhouse: solid body + inset door slab on +Z + overhanging roof slab (privy / tool shed)\n");
     std::printf("  --gen-camp-pack <outDir>\n");
     std::printf("                         Convenience: emit tent + firepit + bedroll + canopy + woodpile + haystack into outDir as 6 .wom files\n");
     std::printf("  --gen-mesh-table <wom-base> [width] [depth] [height] [legThick] [topThick]\n");