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/四足断面/part.yaml

@@ -0,0 +1,74 @@
+id: 四足断面
+original_key: 四足断面
+resource: 半身
+morph_x: 1
+morph_y: 5
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+- x: 0
+  y: 1
+  file: x0y1.svg
+- x: 0
+  y: 2
+  file: x0y2.svg
+- x: 0
+  y: 3
+  file: x0y3.svg
+- x: 0
+  y: 4
+  file: x0y4.svg
+fields:
+- name: 膣基
+- name: 膣壁左
+- name: 膣壁右
+- name: 卵巣左
+- name: 卵管左
+- name: 卵巣右
+- name: 卵管右
+- name: 子宮
+- name: 子宮内
+- name: 子宮口
+- name: 精液
+joints:
+- position: [
+  0.027564282951598268,
+  0.028740295197142426
+]
+- position: [
+  0.03548968984921339,
+  0.02874029519714242
+]
+- position: [
+  0.03152698640040582,
+  0.016297679253218463
+]
+- position: [
+  0.062181567670719494,
+  0.0742074490859955
+]
+- position: [
+  0.06218156767071952,
+  0.06261134446525408
+]
+- position: [
+  0.06915434906547871,
+  0.05813246792084563
+]
+- position: [
+  0.055208786275960285,
+  0.05813246792084563
+]
+- position: [
+  0.05461180784238318,
+  0.0606338591996015
+]
+- position: [
+  0.06975132749905585,
+  0.0606338591996015
+]
+- position: [
+  0.03152698640040582,
+  0.015509463426494025
+]