feat(editor): add --gen-mesh-archery-target training prop

70th procedural mesh primitive. Round-faced archery target on
a 2-post stand:

  • face: closed cylinder along the Z axis (flat ±Z caps face
    the archer line, side wall is the rim) of radius faceR
    centered at height postH
  • stand: 2 vertical posts at the bottom, sized to reach
    from ground to the bottom of the face, with a horizontal
    cross-beam joining them just below the face for rigidity

Concentric scoring rings live in texture space, not geometry —
the cap discs are the natural canvas for a separate target-
ring texture (or use --gen-texture-rings / --gen-texture-
starburst on top).

Pairs naturally with --gen-mesh-training-dummy /
--gen-mesh-fence for sparring grounds, training yards,
militia drill squares, mid-summer fair scenes.

Watertight under weld (verified 198 manifold edges, 0
boundary, 0 non-manifold).

tools/editor/cli_help.cpp

@@ -268,6 +268,8 @@ void printUsage(const char* argv0) {
     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-mesh-archery-target <wom-base> [faceR] [faceT] [sides] [postH] [postW] [beamT]\n");
+    std::printf("                         Archery target: round face cylinder on a 2-post stand with cross-beam (training yard / fair scene)\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-blacksmith-pack <outDir>\n");