feat(editor): add --gen-mesh-podium ceremony-platform primitive

56th procedural mesh: stepped pyramid speaker stand —
configurable number of steps (2..8) tapering from base to top
with equal step heights for visual rhythm, plus a small
lectern box positioned at the back of the top platform so a
speaker has room in front. Top platform is half the base
footprint, with each step shrinking by an equal increment.

Useful for throne rooms, ceremonial dais, NPC speaker
positions, monument bases, judgment platforms. Defaults to
1.60m base × 3 steps with a 0.30m lectern (~0.96m total).

tools/editor/main.cpp

@@ -167,6 +167,7 @@ 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-texture-gradient",
         "--gen-mesh-from-heightmap", "--export-mesh-heightmap",
         "--displace-mesh",