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.

tools/asset_pipeline.py

@@ -258,6 +258,13 @@ def image_paths(values):
     return sorted(set(found))
 
 
+def _variant_output(output: Path, index: int, count: int) -> Path:
+    """Suffix the output path for alternative images (N > 1 only)."""
+    if count <= 1:
+        return output
+    return output.with_name(f"{output.stem}-{index}{output.suffix}")
+
+
 def _generate(args):
     profile = PROFILES[args.role]
     if (args.width is None) != (args.height is None):
@@ -267,21 +274,24 @@ def _generate(args):
     transparent = args.transparent if args.transparent is not None else profile.get(
         "alpha") is True
     prompt = f"{args.prompt.strip()}. {ROLE_GUIDANCE[args.role]}."
-    image = generate_textures.generate_image(
-        prompt, args.model, args.request_size, transparent,
-        aspect_ratio=API_ASPECTS[args.role])
-    foreground = getattr(args, "foreground", None)
-    if foreground:
-        image = colorize_alpha(image, foreground)
-    if args.role == "icon" and has_alpha(image):
-        image = resize_image_from_image(
-            image, width, height, "contain", (0, 0, 0, 0))
-    else:
-        image = ImageOps.fit(image, (width, height),
-                             method=Image.Resampling.LANCZOS)
-    if args.role == "tile":
-        image = make_seamless(image)
-    save_image(image, resolve_path(args.output))
+    count = max(1, int(getattr(args, "variants", 1) or 1))
+    output = resolve_path(args.output)
+    for index in range(1, count + 1):
+        image = generate_textures.generate_image(
+            prompt, args.model, args.request_size, transparent,
+            aspect_ratio=API_ASPECTS[args.role])
+        foreground = getattr(args, "foreground", None)
+        if foreground:
+            image = colorize_alpha(image, foreground)
+        if args.role == "icon" and has_alpha(image):
+            image = resize_image_from_image(
+                image, width, height, "contain", (0, 0, 0, 0))
+        else:
+            image = ImageOps.fit(image, (width, height),
+                                 method=Image.Resampling.LANCZOS)
+        if args.role == "tile":
+            image = make_seamless(image)
+        save_image(image, _variant_output(output, index, count))
 
 
 def resize_image_from_image(image, width, height, fit, background):
@@ -365,6 +375,9 @@ def build_parser():
                           default=generate_textures.GEN_SIZE)
     generate.add_argument("--width", type=int)
     generate.add_argument("--height", type=int)
+    generate.add_argument("--variants", type=int, default=1,
+                          help="generate N alternative images; saved as "
+                               "<stem>-1.png ... <stem>-N.png when N > 1")
     generate.add_argument(
         "--foreground", type=parse_color,
         help="replace visible RGB with this color while preserving alpha")