Generated gear parts (helmet, shoulder pieces, crown, cape, horns, plume) instead of drawn shapes

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

art/generated/gear/PROMPTS.md

@@ -0,0 +1,12 @@
+# Gear parts (high-res)
+
+The parts laid over the detailed sprites as their gear (helmet, shoulder piece, crown, cape,
+horn, plume; `GEAR_*` and `gen_gear` in `src/gfx.rs`). Generated on 2026-11-08 with
+`fal-ai/nano-banana-pro` (`aspect_ratio: 3:2`, `resolution: 2K`, one image), the prompt in
+`batch.py`: six pieces in light neutral grey on magenta, so the game tints them (bronze, steel,
+gold; the cape red for creatures, blue for heroes).
+
+Processing (inline python, see the session): magenta keyed out, every piece cropped to its
+picture, the horn mirrored, turned into light grey (luminance x 1.25), scaled to its place in the
+gear texture (the old rects times four: helmet 96x48, shoulder 48x36, crown 80x40, cape 112x160,
+horn 28x40, plume 28x48) with hard alpha; copied to `assets/textures/gear/<part>.png`.