feat(editor): add --gen-texture-blueprint drafting-paper grid

63rd procedural texture: minor + major grid lines on a base.
Minor lines at every `minorStride` pixels (default 16);
every `majorEvery` minor lines a thicker major line is drawn
(default every 4). Both axes get the same treatment so the
result is a sectioned drafting / engineer's paper look.

Distinct from --gen-texture-mesh-screen (uniform line
weight) — this is the periodic-emphasis variant. Good for:

  • drafting-table surfaces
  • technical-schematic backdrops
  • architect-shop / cartographer-shop walls
  • engineer / scholar ritual tables
  • star-chart room floors

Default 16-stride / every-4-major gives the classic blue
graph-paper aesthetic at 256x256. First procedural texture
that takes 4 numeric layout params plus W/H — exercises the
new parseOpt* helpers across more args than usual.

tools/editor/cli_arg_required.cpp

@@ -97,6 +97,7 @@ const char* const kArgRequired[] = {
     "--gen-texture-carbon", "--gen-texture-pinstripe",
     "--gen-texture-camo", "--gen-texture-snake-skin",
     "--gen-texture-mesh-screen", "--gen-texture-bamboo",
+    "--gen-texture-blueprint",
     "--validate-glb", "--info-glb", "--info-glb-tree", "--info-glb-bytes",
     "--validate-jsondbc", "--check-glb-bounds", "--validate-stl",
     "--validate-png", "--validate-blp",