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/四足胸郭/part.yaml

@@ -0,0 +1,72 @@
+id: 四足胸郭
+original_key: 四足胸郭
+resource: 半身
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 胸郭
+- name: 筋肉
+- name: 紋柄
+- name: 虎柄
+- name: 鱗
+joints:
+- position: [
+  0.49589714095965687,
+  0.41992859916794767
+]
+- position: [
+  0.5041022495456186,
+  0.41992943152871176
+]
+- position: [
+  0.48150199968557955,
+  0.45056696335020374
+]
+- position: [
+  0.5184967409774262,
+  0.45056696335020374
+]
+- position: [
+  0.4865229115244023,
+  0.5098738164535057
+]
+- position: [
+  0.5134752041801278,
+  0.5098738164535059
+]
+- position: [
+  0.4999990747804779,
+  0.5016008098797703
+]
+- position: [
+  0.47783318744584347,
+  0.4381679830329647
+]
+- position: [
+  0.5221649479777382,
+  0.4381679830329647
+]
+- position: [
+  0.4999990493881583,
+  0.5243527109272514
+]
+- position: [
+  0.49999987927198636,
+  0.4726748080603186
+]
+- position: [
+  0.47783318744584347,
+  0.47230634681171996
+]
+- position: [
+  0.5221649479777382,
+  0.47230634681171996
+]
+- position: [
+  0.015058466988291011,
+  0.024008396645510584
+]