Phase 0.3-0.5: SVG export + YAML sidecars + asset catalog

- Add hair class KeyMap entries (基髪→BaseHair, 前髪→FrontHair, 胸毛→ChestHair)
- Implement cardinal spline → cubic Bezier SVG export for all 175 body parts
- Generate YAML sidecar files (part.yaml) per part with metadata
- Write Catalog.yaml index for runtime asset loading
- Output to SlaveMatrix/Assets/Parts/{EnglishName}/ structure
- Each part directory contains part.yaml + x{x}y{y}.svg morph variants
- 838 SVGs across 324 morph variants, 175 sidecars, 1 catalog
- Extraction tool now serves as the asset build pipeline step

SlaveMatrix/Assets/Parts/Torso/part.yaml

@@ -0,0 +1,47 @@
+id: Torso
+original_key: 胴
+resource: 胴体
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 胴
+- name: 筋肉
+- name: 獣性
+- name: 植タトゥ
+joints:
+- position: [
+  0.5,
+  0.525925439940814
+]
+- position: [
+  0.49084942215127053,
+  0.531891026214109
+]
+- position: [
+  0.5091505778487299,
+  0.531891026214109
+]
+- position: [
+  0.47950612315817276,
+  0.5342460034502376
+]
+- position: [
+  0.5204938768418274,
+  0.5342460034502376
+]
+- position: [
+  0.5000000000000002,
+  0.531891026214109
+]
+- position: [
+  0.011819984866887245,
+  0.0048159168484769345
+]
+- position: [
+  0.0016388137072666491,
+  0.0048159168484769345
+]