Extend AI image tooling with variants; drop dev asset folders from git

asset_pipeline generate gains --variants N (saved as <stem>-1..N.png). .gitignore now excludes assets/models/concepts, assets/models/npc, assets/textures/npc/ai, and raw assets/textures/ai outputs; only game_ready and the game-facing NPC maps/models stay tracked.

MEMORY.md

@@ -46,6 +46,16 @@ Session memory for durable decisions, state, and gotchas. Keep concise, remove o
   Next: Phase 3 (`NpcAvatar._load_model` + slot tinting) consumes
   `palette.json` and the GLB; Phase 2's capture/judge item is blocked on that.
 
+- **Git hygiene + tooling (2026-11-01):** dev asset folders are now gitignored
+  and untracked: `assets/models/concepts/`, `assets/models/npc/` (Blender
+  sources), `assets/textures/npc/ai/` (raw AI fabrics), and the raw
+  `assets/textures/ai/*` outputs (only `assets/textures/ai/game_ready/` stays).
+  Kept in the repo: `assets/textures/npc/*_{albedo,normal,orm}.png` +
+  `palette.json`, `assets/models/generated/*` (props + npc_base.glb), and the
+  authored `assets/textures/*` set. `tools/asset_pipeline.py generate` gained
+  `--variants N` — generates N alternatives saved as `<stem>-1..N.png` (N=1
+  keeps the unsuffixed path). Python tooling tests still pass (exit 0).
+
 - Repo: `/run/media/system/DATA/Documents/06-games/security-game` (also reachable at
   `/var/home/zwitschi/Documents/06-games/security-game`). Godot: `~/.local/bin/godot` (4.3.stable).
   Tests: `godot --headless --path . --script res://src/test/test_runner.gd` → **177/177**.