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_help.cpp

@@ -151,6 +151,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Carbon-fiber: 2x2 alternating-orientation weave with sin² fiber highlights (sci-fi/tech panels)\n");
     std::printf("  --gen-texture-pinstripe <out.png> <bgHex> <lineHex> [stride] [lineW] [featureEvery] [W H]\n");
     std::printf("                         Pinstripe: thin vertical lines at every stride; every Nth stripe is doubled-thick feature line\n");
+    std::printf("  --gen-texture-camo <out.png> <aHex> <bHex> [cellSize] [threshold] [seed] [W H]\n");
+    std::printf("                         Camouflage: 2-octave value noise thresholded into hard bg/fg blobs (woodland disruption pattern)\n");
     std::printf("  --add-texture-to-zone <zoneDir> <png-path> [renameTo]\n");
     std::printf("                         Copy an existing PNG into <zoneDir> (optionally renaming it on the way in)\n");
     std::printf("  --gen-mesh <wom-base> <cube|plane|sphere|cylinder|torus|cone|ramp> [size]\n");