feat: Taila — second anime character through a hardened import pipeline

New selectable skin: Taila (original anime character by Partaevil,
CC-BY, license kept alongside the model), cel-shaded with ink outlines,
running the full 18-clip animation set + the new rifle-hold pose layer.

Pipeline hardening learned the hard way (each of these produced a broken
character before the fix):
- tools/strip_rig.py: strips a foreign rig (VRoid/Mixamo names bake FLAT
  clips in the name-based retarget), keeps only meshes skinned to that rig
  (scene props were joining into the player model), recentres feet-on-origin,
  and reroutes image textures into Principled base color for re-export.
- tools/unlit_to_pbr.py: KHR_materials_unlit anime models carry their albedo
  in emissiveTexture over a black base — Blender 5.1 drops the texture on
  import, rendering the character pitch black. Rewrites the GLB JSON to
  standard textured PBR before Blender ever sees it.

Also dropped the Elle import attempt: her rest pose is seated (posed scene),
which the T-pose autorig cannot use.

Co-Authored-By: Claude Fable 5 <[email protected]>

assets/characters/skins/skins.json

@@ -6,6 +6,13 @@
       "description": "Hatsune Miku \u2014 Virtual Idol",
       "model": "res://assets/characters/skins/miku.glb",
       "unlocked": true
+    },
+    {
+      "id": "taila",
+      "name": "Taila",
+      "description": "Original anime character by Partaevil (CC-BY)",
+      "model": "res://assets/characters/skins/taila.glb",
+      "unlocked": true
     }
   ]
 }

assets/characters/skins/taila.license.json

@@ -0,0 +1,9 @@
+{
+  "name": "Taila | Original work",
+  "uid": "8ae231b61fc34827be30e2a1edc5b811",
+  "author": "Partaevil",
+  "author_url": "https://sketchfab.com/Partaevil",
+  "license": "CC Attribution",
+  "license_slug": "by",
+  "source_url": "https://sketchfab.com/3d-models/taila-original-work-8ae231b61fc34827be30e2a1edc5b811"
+}