feat: swap the figure to the Mixamo anatomical mannequin

Replace Michelle with the anatomical mannequin character (owner-exported
Mixamo FBX): neutral, unclothed anatomy with visible musculature suits
the physio/fitness content better than a fashion character, and the
optimized GLB is 702KB vs 2.2MB (35MB source FBX -> FBX2glTF -> WebP
textures + quantization + stripped animations).

- character.ts: tolerate numbered Mixamo namespaces (mixamorig1:...)
  emitted by direct Mixamo exports.
- Regenerate all four README GIFs with the new figure.
- README: update the character attribution.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0155HaTaobTF48hVWvJwhj8h

Author: claude

README.md

@@ -124,7 +124,7 @@ Two safety layers ship with the language:
 The protocol and both libraries are **MIT-licensed**: the open core. See [`spec/SPEC.md`](spec/SPEC.md) for the full language and [`spec/llm-authoring.md`](spec/llm-authoring.md) for the authoring prompt.
 For where Posecode spreads fastest and the per-domain go-to-market plan, see [`docs/market-research.md`](docs/market-research.md); for the engine roadmap, [`ROADMAP.md`](ROADMAP.md).
 
-The realistic 3D character ("Michelle") is an [Adobe Mixamo](https://www.mixamo.com) asset, distributed with the [three.js examples](https://github.com/mrdoob/three.js/tree/dev/examples/models/gltf) and used here under the Mixamo license (royalty-free in projects). The renderer also ships a zero-asset procedural figure, used automatically wherever the character can't load.
+The 3D figure is the [Adobe Mixamo](https://www.mixamo.com) anatomical mannequin character, exported from Mixamo and used under the Mixamo license (royalty-free in projects). The renderer also ships a zero-asset procedural figure, used automatically wherever the character can't load — and it accepts any Mixamo-rigged GLB via `characterUrl`.
 
 ---
 

docs/media/deadlift.gif

@@ -79,9 +79,13 @@ const Y_UP = new THREE.Vector3(0, 1, 0);
 const Y_DOWN = new THREE.Vector3(0, -1, 0);
 const Z_FWD = new THREE.Vector3(0, 0, 1);
 
-/** Strip the mixamo namespace: "mixamorig:LeftArm"/"mixamorigLeftArm" → "LeftArm". */
+/**
+ * Strip the mixamo namespace: "mixamorig:LeftArm", "mixamorigLeftArm", and
+ * numbered re-exports like "mixamorig1:LeftArm" all → "LeftArm". (Colons are
+ * already removed by GLTFLoader's name sanitizer at runtime.)
+ */
 function plainName(name: string): string {
-  return name.replace(/^mixamorig:?/i, "");
+  return name.replace(/^mixamorig\d*:?/i, "");
 }
 
 interface MappedBone {