Completes the texture-family extraction started in 6ea2dfcf.
Moves the 11 older simpler texture handlers (gradient, noise,
noise-color, radial, stripes, dots, rings, checker, brick, wood,
grass, fabric) into the existing cli_gen_texture.cpp module.
Each previously had its own ~30-line copy of parseHex; all now
use the shared helper at file scope.
Also fixed a pre-existing match-order issue: the dispatcher
checks --gen-texture-noise-color before --gen-texture-noise so
the prefix-match doesn't shadow the longer name.
main.cpp drops 25,494 → 24,270 lines (-1,224). All 19 texture
generators (12 just-extracted + 7 from the previous batch) now
live in their own translation unit. Behavior verified by
re-running gradient/noise/noise-color/checker/fabric.
Moves the Worley/cellular-noise-based texture handlers
(--gen-texture-cobble, -marble, -metal, -leather, -sand,
-snow, -lava) into their own translation unit. Each handler
previously had its own ~33-line copy of the parseHex lambda;
all 7 copies are replaced with a single shared parseHex
helper at file scope.
Older simpler generators (gradient/noise/radial/stripes/dots/
rings/checker/brick/wood/grass/fabric) still live in main.cpp
and will be migrated in subsequent batches.
main.cpp drops 26,286 → 25,494 lines (-792). Behavior
unchanged across all 7 handlers (re-verified).
