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/留具後/part.yaml

@@ -0,0 +1,47 @@
+id: 留具後
+original_key: 留具後
+resource: 胴体
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 革左
+- name: 革右
+- name: 丸金具1
+- name: 革
+- name: 丸金具2
+- name: 丸金具3
+- name: 丸金具4
+- name: 丸金具5
+joints:
+- position: [
+  0.0077616083391022295,
+  -0.006534929681779852
+]
+- position: [
+  0.011108172588731634,
+  0.008494752163690982
+]
+- position: [
+  0.014544399969939016,
+  -0.003245981324756838
+]
+- position: [
+  0.011159007937725165,
+  0.01201721664159386
+]
+- position: [
+  0.011196563353453298,
+  0.002513407933153138
+]
+- position: [
+  0.007398070423497567,
+  0.016910523688056147
+]
+- position: [
+  0.014907469381300685,
+  0.016910523688056147
+]