feat(editor): add --gen-texture-moon disc with phase shadow

82nd procedural texture: solid filled circle of moonHex on
bg, with an optional crescent shadow created by subtracting
a second bg-colored disc offset by `phase` pixels along +X.

Phase reads as the lunar-cycle moment:
  • phase = 0           — full moon
  • 0 < phase < moonR    — gibbous (waning right)
  • phase = moonR        — half moon
  • phase > moonR        — crescent (thinner as phase grows)

Useful for night-sky overlays, banner moons (heraldry of
night-themed orders), shrine medallion centers, druid /
priest emblem inserts, lunar-festival decoration, vampire-
zone backdrops.

The simplest centered-disc texture in the catalogue —
pairs naturally with --gen-texture-stars for a complete
night-sky composite.

tools/editor/cli_help.cpp

@@ -197,6 +197,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Halftone: grid of dots whose radii grow with a v/h/r gradient (comic / newspaper print look)\n");
     std::printf("  --gen-texture-bayer <out.png> <aHex> <bHex> [cellSize] [W H]\n");
     std::printf("                         Bayer: 4x4 ordered-dither matrix tiled (retro / 8-bit / monochrome-CRT effects)\n");
+    std::printf("  --gen-texture-moon <out.png> <bgHex> <moonHex> [moonR] [phase] [W H]\n");
+    std::printf("                         Moon disc with optional crescent shadow (phase 0=full, =moonR=half, >moonR=crescent)\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");