feat(editor): add --gen-mesh-crate-stack scene primitive

63rd procedural mesh primitive. The first to explicitly
compose a *scene* of multiple objects rather than a single
structure: an N×M×K arrangement of cube crates with a small
gap between each so they read as discrete shipping boxes
rather than one merged solid.

Default 2×2×2 = 8 crates with 0.40 m sides on a 0.02 m gap
gives a tight pyramidal pile. Larger configurations (e.g.
4×3×2 = 24 crates) read as warehouse pallets.

Uses every shared helper added this batch — addFlatBox for
each crate, finalizeAsSingleBatch for the trailing batch,
stripExt for the .wom suffix, parseOptInt/Float for the
optional dimension args. Each crate emits the standard
24-vert / 12-tri box, so an N×M×K stack is a clean
N*M*K-multiple in vertices and triangles.

Useful for warehouses, cargo holds, dock loading bays,
market stalls, dwarven mining caches, pirate stash piles.
Watertight under weld — the gap keeps adjacent crates
from sharing corner positions.

tools/editor/cli_help.cpp

@@ -240,6 +240,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Bedroll: horizontal closed cylinder along Z axis with optional pillow box at +Z (camp set dressing)\n");
     std::printf("  --gen-mesh-workbench <wom-base> [length] [depth] [height] [legR] [topT] [viseSize] [trayH]\n");
     std::printf("                         Workbench: 4-legged top slab with optional vise at +X end and back tool tray (blacksmith / crafter)\n");
+    std::printf("  --gen-mesh-crate-stack <wom-base> [crateSize] [columns] [rows] [layers] [gap]\n");
+    std::printf("                         Crate stack: N×M×K cube grid with small gap between crates (warehouses, cargo holds, dockyards)\n");
     std::printf("  --gen-mesh-table <wom-base> [width] [depth] [height] [legThick] [topThick]\n");
     std::printf("                         Table: flat top slab on 4 corner legs (default 1.6/1.0/0.85/0.10/0.06)\n");
     std::printf("  --gen-mesh-lamppost <wom-base> [poleH] [poleT] [baseSize] [lanternSize] [lanternH]\n");