feat(editor): add --gen-texture-shingles roof-tile pattern

35th procedural texture: roof shingles done as half-row-staggered
rows of rectangular tiles. Three colors: shingle base, a shadow
band at the top of each row (where the row above overlaps), and
thin vertical seams between adjacent shingles in the same row.

The half-row stagger comes from the standard roofing convention
of offsetting alternate courses by half a tile width — gives the
classic interlocked look that pure brick patterns lack.

Useful for roofs, scale armor close-ups, fish bellies, anywhere
needing tightly-packed offset rectangles. Defaults to 32x24
shingles with 4-px shadow + 1-px seams.

tools/editor/cli_help.cpp

@@ -103,6 +103,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Scales: half-row-staggered overlapping circles forming fish/dragon/chain-mail look\n");
     std::printf("  --gen-texture-stained-glass <out.png> <leadHex> <colorAHex> <colorBHex> <colorCHex> [cells] [W H]\n");
     std::printf("                         Stained glass: Voronoi cells in 3-color rotation, separated by dark lead lines\n");
+    std::printf("  --gen-texture-shingles <out.png> <baseHex> <shadowHex> <seamHex> [shingleW] [shingleH] [shadowH] [W H]\n");
+    std::printf("                         Roof shingles: half-offset rows of rectangular tiles with shadow band + vertical seams\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");