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/紅潮/part.yaml

@@ -0,0 +1,41 @@
+id: 紅潮
+original_key: 紅潮
+resource: 胴体
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 紅潮0
+- name: 紅潮1
+- name: 紅潮右
+- name: 紅潮左
+- name: 紅潮線左
+- name: 紅潮線右
+- name: 紅潮弱左
+- name: 紅潮弱右
+- name: 紅潮線弱左
+- name: 紅潮線弱右
+joints:
+- position: [
+  0.011152769902399134,
+  0.008664148248209158
+]
+- position: [
+  -0.005758724011670753,
+  0.009373590903165892
+]
+- position: [
+  0.028064263816469006,
+  0.009373590903165889
+]
+- position: [
+  0.01944782392164254,
+  0.01201685996646432
+]
+- position: [
+  0.0028577158831557432,
+  0.012016859966464321
+]