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]>

tools/verify_character.py

@@ -58,8 +58,8 @@ warnings = []
 weights_authored = True
 
 
-def check(ok, label, detail="", needs_authored_weights=False):
-    soft = needs_authored_weights and not weights_authored
+def check(ok, label, detail="", needs_authored_weights=False, advisory=False):
+    soft = advisory or (needs_authored_weights and not weights_authored)
     tag = "PASS" if ok else ("WARN" if soft else "FAIL")
     print(f"  [{tag}] {label}" + (f" — {detail}" if detail else ""))
     if ok:
@@ -134,8 +134,20 @@ check(bleed_frac < 0.005, "cross-leg blending is limited to draping cloth",
 check(four < 0.5, "influences look authored, not solved",
       f"{four * 100:.0f}% of verts carry 4 influences; spread {dict(sorted(infl.items()))}",
       needs_authored_weights=True)
-check(len(meshes) > 1, "model keeps its per-part meshes", f"{len(meshes)} meshes",
-      needs_authored_weights=True)
+# ADVISORY, not a gate. Several meshes is what we want — it is how body, cloth
+# and hair stay separable for materials, for the outline pass and for the cloth
+# solver's hull extraction — but the OUTPUT cannot tell "the pipeline joined
+# them" from "the artist authored one mesh". Quaternius' mannequin is a single
+# mesh on purpose and was failing a check about damage that had not happened.
+#
+# The join path leaves two signatures that ARE unambiguous, and both are hard
+# checks above: cross-leg weight bleed, and the 4-influences-everywhere spread
+# of a nearest-bone rebind. Those catch what this was standing in for.
+check(len(meshes) > 1, "model keeps its per-part meshes",
+      f"{len(meshes)} mesh{'es' if len(meshes) != 1 else ''}"
+      + (" — fine for a single-piece model; a costume should be several"
+         if len(meshes) == 1 else ""),
+      advisory=True)
 
 # ------------------------------------------------------------------- skeleton
 def is_rootish(b):