feat(editor): add --gen-mesh-mortar-pestle alchemy primitive

90th procedural mesh: a wider-than-tall closed cylinder
(the mortar bowl) with a thin tall closed cylinder (the
pestle) rising from its center. Bowl reads as carved stone
or wood; pestle reads as a small grinding rod centered in
the rim.

Distinct from existing kitchenware primitives:
  • --gen-mesh-cauldron — large + has supporting legs
  • --gen-mesh-chalice  — 3-tier goblet, no separate utensil
  • --gen-mesh-mug      — handled drinking cup
  • --gen-mesh-bowl     — does not exist; this primitive
                          covers the small-bowl + tool case

Useful for: alchemy lab counters, kitchen / cooking-stove
dressing, herbalist shop interiors, witchcraft NPCs,
quest-giver desks for "grind these herbs" objectives.

124 verts / 112 tris at default 14 sides — two simple
closed cylinders sharing a single batch with shared
texture coords.

tools/editor/cli_arg_required.cpp

@@ -77,7 +77,7 @@ const char* const kArgRequired[] = {
     "--gen-mesh-lantern", "--gen-mesh-chalice",
     "--gen-mesh-standing-torch", "--gen-mesh-scroll-case",
     "--gen-mesh-stove", "--gen-mesh-well-pail",
-    "--gen-mesh-mug",
+    "--gen-mesh-mug", "--gen-mesh-mortar-pestle",
     "--gen-camp-pack", "--gen-blacksmith-pack", "--gen-village-pack",
     "--gen-temple-pack", "--gen-graveyard-pack",
     "--gen-garden-pack", "--gen-dock-pack", "--gen-tavern-pack",