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/意思表示/part.yaml

@@ -0,0 +1,54 @@
+id: 意思表示
+original_key: 意思表示
+resource: 胴体
+morph_x: 1
+morph_y: 4
+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
+fields:
+- name: 吹出し
+- name: 怒
+joints:
+- position: [
+  0.13992925487475652,
+  0.12517489401430398
+]
+- position: [
+  0.018657236965027572,
+  0.014689071649392193
+]
+- position: [
+  0.036380226823476636,
+  0.014689071649392193
+]
+- position: [
+  0.0351032961126059,
+  0.04491598303972058
+]
+- position: [
+  0.05472866996683526,
+  0.04491598303972058
+]
+- position: [
+  0.095,
+  0.0809416624195675
+]
+- position: [
+  0.08616939871158194,
+  0.0731107726424042
+]
+- position: [
+  0.09221099875808295,
+  0.09215345518156899
+]