feat(editor): add --gen-texture-camo woodland-disruption pattern

59th procedural texture: 2-octave bilinear value noise
thresholded into hard bg/fg blobs. Sharp edges read as
real military camouflage rather than the smooth gradient
--gen-texture-noise-color produces.

Two octaves combined at 0.7/0.3 weights:
  • low frequency at cellSize lattice → large dominant blobs
  • high frequency at cellSize/4 lattice → finer mottling
    overlay so blob edges aren't perfectly smooth

Threshold parameter shifts the bg/fg balance — lower values
expose more accent color (good for leaf-pattern), higher
values keep the dominant color dominant (good for rock/sand).

Useful for guard cloaks, military uniforms, ghillie suits,
druid robes, hunter blinds, scout cloaks. First procedural
texture to use the new savePngOrError helper from
cli_png_emit.hpp.

tools/editor/cli_arg_required.cpp

@@ -92,6 +92,7 @@ const char* const kArgRequired[] = {
     "--gen-texture-starburst", "--gen-texture-studs",
     "--gen-texture-moss", "--gen-texture-woodgrain",
     "--gen-texture-carbon", "--gen-texture-pinstripe",
+    "--gen-texture-camo",
     "--validate-glb", "--info-glb", "--info-glb-tree", "--info-glb-bytes",
     "--validate-jsondbc", "--check-glb-bounds", "--validate-stl",
     "--validate-png", "--validate-blp",