feat(characters): import the Quaternius mannequin as a selectable skin

A third playable character, built with the pipeline skill from a source
that was already in the repo: the animation library ships a rigged
Mannequin mesh on the exact 53-joint reference skeleton, CC0, so it needed
no download and retargets perfectly. 18 clips, 0.3% cross-leg bleed, 7% of
verts at four influences — a clean authored-weight import. Licence
recorded in mannequin.license.json as the other skins do.

It has no cloth chains, correctly: it is a mannequin and has neither hair
nor clothes.

Importing it turned up two real bugs, both of which would have hit any
flat-coloured or single-piece model:

- LevelMaterials.apply_character_look treated ANY untextured surface on a
  character as the model's own outline shell and hid it, so the mannequin
  rendered as a solid black silhouette — its body and joint materials are
  untextured flat colours, not ink. _is_line_work() now asks whether the
  surface is named eyes*, is drawn front-face-culled (the inverted-hull
  setup), or is near-black. Taila and Miku are unaffected: their materials
  are textured and never reach that branch. Verified by render.

- verify_character.py failed the build for having one mesh. That check
  cannot tell "the pipeline joined them" from "the artist authored one
  mesh" — Quaternius' mannequin is one piece on purpose. It is advisory
  now; the join path's two unambiguous signatures, cross-leg bleed and the
  4-influences-everywhere spread, are still hard checks.

Also restored Miku's description, which the re-import had blanked.

3 GLB skins selectable (6 with the built-in colour skins). Smoke 0
failures, 11/11 movement tests, cloth idle 0.024-0.078 deg/frame.

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

.claude/skills/character-pipeline/references/stylization.md

@@ -19,8 +19,16 @@ Toon-lighting that shell is what put a **white rim on every hair strand**. It is
 an inverted hull whose normals face away from you; a lighting model that adds a
 rim term lights it brightly exactly where it is supposed to read as ink.
 
-`apply_character_look` therefore treats **any untextured surface on a character**
-as the model's own line-work and handles it flat and unshaded:
+`apply_character_look` therefore looks for the model's own line-work and handles
+it flat and unshaded. "Untextured" alone is NOT the test — that made every
+flat-coloured model render as a black silhouette, because Quaternius' mannequin
+has two untextured materials (a yellow body, lilac joints) and both were hidden
+as though they were an outline shell. `_is_line_work()` asks three things
+instead: is it named `eyes*`, is it drawn front-face-culled (the classic
+inverted-hull setup), or is its albedo near-black. An ink shell is black; a
+flat-coloured character is any colour at all.
+
+What it then does:
 
 - **Outline hull** → made fully transparent rather than deleted. Deleting a
   surface would renumber the rest and break the mesh's own skin bindings. The
@@ -28,9 +36,15 @@ as the model's own line-work and handles it flat and unshaded:
 - **Eye cards** (`resource_name` starts with `eyes`) → flat ink, except anything
   with `HL` in the name, which is the glint in the pupil and really is white.
 
-If a newly imported character comes out with a white halo, or with black eyes
-that should have irises, this function and its name-matching are where to look —
-the naming conventions vary by source and this is the one place they are read.
+If a newly imported character comes out with a white halo, a black silhouette,
+or black eyes that should have irises, `_is_line_work()` and the name-matching
+below it are where to look. The conventions vary by source and this is the one
+place they are read.
+
+Taila's eyes still render as black cards rather than amber irises. Her eye
+surfaces are untextured, and the glTF import hands every untextured surface a
+default near-white albedo, so colour cannot tell an iris card from a lash card
+on her — the name is all there is, and `eyes*` currently means "ink". Unfixed.
 
 ## Materials on import: the unlit problem