Rewrite puppet load_textures for atlas-handle + uv

Bones now reference atlas-uv rectangles instead of holding per-bone
texture handles. The rig gains an atlas record with a single diffuse
texture handle plus a tiles-by-name dictionary for bone-name lookup.
Bone-draw uses the ADR-0044 source-rect render primitive. Anchor
defaults to tile UV center; rig-level b.anchor overrides. Bumps lib
to 0.5.0 to flag the breaking change in rig.bones shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

manifest.lib

@@ -1,6 +1,6 @@
 {
     "id": "lib-core.puppet",
-    "version": "0.4.4",
+    "version": "0.5.0",
     "api_min": "0.1",
     "deps": []
 }