feat(editor): add --gen-texture-plaid translucent-bands pattern

65th procedural texture: 2 sets of parallel "translucent"
bands — one horizontal, one vertical — overlaid on a base.
Each band contributes 0.5 alpha, so where bands cross both
half-alphas combine for the darkest color (the unmistakable
plaid grid intersection).

Distinct from --gen-texture-tartan (3-4 colors with
asymmetric stripe pitches) — this is the simple symmetric
2-color variant. Distinct from --gen-texture-checker (hard
binary squares) — plaid uses 3-tone alpha-blend gradient.

Useful for pub-table cloths, country-tavern napery, dwarven
formal-attire trim, picnic blankets, peasant-clothier
swatches. Default 24-stride / 8-band reads as classic
country-checked at 256x256.

First procedural texture to also use the new printPngWrote
helper from this batch.

tools/editor/cli_help.cpp

@@ -163,6 +163,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Blueprint: minor + major grid lines (technical drawing / drafting paper / engineer's table)\n");
     std::printf("  --gen-texture-rust-streaks <out.png> <bgHex> <rustHex> [streakCount] [seed] [W H]\n");
     std::printf("                         Rust streaks: vertical drip bands fading down from hash-jittered tops (weathered metal / hull stains)\n");
+    std::printf("  --gen-texture-plaid <out.png> <bgHex> <bandHex> [stride] [bandW] [W H]\n");
+    std::printf("                         Plaid: 2 sets of crossed translucent bands; intersections darken via combined half-alpha\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");