feat(editor): add --gen-mesh-forge blacksmith hearth

69th procedural mesh primitive. Built from up to 3 axis-
aligned boxes:

  • stone hearth: rectangular base spanning width × depth ×
    baseH, where the smith's fire would sit
  • hood: smaller smoke-collector box on top of the hearth,
    inset by hoodInset on each side so it reads as the
    chimney's flared base
  • optional thin chimney rising from the hood — set
    chimneyH=0 for an open-vented forge

Pairs naturally with --gen-mesh-anvil and
--gen-mesh-workbench for blacksmith/armorer/farrier scenes,
and with --gen-mesh-bench / --gen-mesh-crate-stack for
the storage corner of a smithy.

Watertight under weld (verified 54 manifold edges, 0
boundary, 0 non-manifold). Default 1.4×1.0×0.9 m hearth +
0.5 m hood + 1.2 m chimney reads as a normal village smithy.

tools/editor/cli_help.cpp

@@ -264,6 +264,8 @@ void printUsage(const char* argv0) {
     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-mesh-forge <wom-base> [width] [depth] [baseH] [hoodH] [hoodInset] [chimneyH] [chimneyW]\n");
+    std::printf("                         Blacksmith forge: stone hearth + smaller hood + optional chimney (smithy / armorer set dressing)\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");