feat(editor): add --gen-mesh-brazier fire-pit primitive

57th procedural mesh: 7-box brazier — square base plate,
narrow vertical stem, wider bowl on top of the stem, and 3
flame boxes of varying heights rising from the bowl. The
flame layout is a triangle (tallest center, two shorter on
either side) so the silhouette reads as fire rather than a
uniform block.

Useful for dungeons, temples, watchtowers, throne rooms,
goblin camps — anywhere a fantasy world needs visible light
sources. Defaults to 0.55m bowl on a 0.80m stem (~1.28m
total height).

tools/editor/main.cpp

@@ -168,7 +168,7 @@ int main(int argc, char* argv[]) {
         "--gen-mesh-stool", "--gen-mesh-cauldron", "--gen-mesh-gate",
         "--gen-mesh-beehive", "--gen-mesh-weathervane",
         "--gen-mesh-scarecrow", "--gen-mesh-sundial",
-        "--gen-mesh-podium",
+        "--gen-mesh-podium", "--gen-mesh-brazier",
         "--gen-texture-gradient",
         "--gen-mesh-from-heightmap", "--export-mesh-heightmap",
         "--displace-mesh",