feat(editor): add --gen-texture-tile square stone tile pattern

Per-cell pattern: each pixel falls into a tile cell with grout
on every grid edge. Tiles get a stable per-tile shade jitter
(via integer-cell hash) so adjacent tiles look distinct rather
than identical. Grout is the constant separator color.

First new texture added directly to cli_gen_texture.cpp instead
of main.cpp — proves the modular pattern works for new
additions, not just extractions.

Defaults: tilePx=32, groutPx=2. Useful for floors, plaza
paving, dungeon walls. Brings the procedural texture pattern
set to 23.

tools/editor/cli_help.cpp

@@ -73,6 +73,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Snow: soft cool-white base + scattered bright sparkle pixels (default density=0.005)\n");
     std::printf("  --gen-texture-lava <out.png> <darkHex> <hotHex> [seed] [crackScale] [W H]\n");
     std::printf("                         Lava: dark cooled crust with bright glowing cracks via Worley cell boundaries\n");
+    std::printf("  --gen-texture-tile <out.png> <tileHex> <groutHex> [tilePx] [groutPx] [W H]\n");
+    std::printf("                         Square stone tiles with grout grid (default 32px tiles, 2px grout)\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");