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/四足染み/part.yaml

@@ -0,0 +1,62 @@
+id: 四足染み
+original_key: 四足染み
+resource: その他
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 潮1
+- name: 潮2
+- name: 潮3
+- name: 尿1
+- name: 尿2
+- name: 汗
+- name: 湯気
+joints:
+- position: [
+  0.2775277367793258,
+  0.2673779032672849
+]
+- position: [
+  0.27752773677932585,
+  0.30381436492321273
+]
+- position: [
+  0.34744901594506805,
+  0.38181830645607867
+]
+- position: [
+  0.34744901594506805,
+  0.4231961056345822
+]
+- position: [
+  0.33467017873915106,
+  0.3211995973988318
+]
+- position: [
+  0.34431444163765135,
+  0.3325224543213954
+]
+- position: [
+  0.32968722181715443,
+  0.3151730084663655
+]
+- position: [
+  0.33447471851947264,
+  0.31371797961326753
+]
+- position: [
+  0.3539587045361517,
+  0.3211995973988318
+]
+- position: [
+  0.3589416614581483,
+  0.3151730084663655
+]
+- position: [
+  0.3541541647558301,
+  0.31371797961326753
+]