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/呼気/part.yaml

@@ -0,0 +1,48 @@
+id: 呼気
+original_key: 呼気
+resource: 胴体
+morph_x: 1
+morph_y: 2
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+- x: 0
+  y: 1
+  file: x0y1.svg
+fields:
+- name: 呼気左1
+- name: 呼気左2
+- name: 呼気左3
+- name: 呼気右1
+- name: 呼気右2
+- name: 呼気右3
+joints:
+- position: [
+  0.3344464727836933,
+  0.3345962358494053
+]
+- position: [
+  0.34431444163765135,
+  0.3325224543213954
+]
+- position: [
+  0.3384660967986369,
+  0.33969153389651674
+]
+- position: [
+  0.33189882376013763,
+  0.33969153389651674
+]
+- position: [
+  0.35418241049160937,
+  0.3345962358494053
+]
+- position: [
+  0.3501627864766659,
+  0.33969153389651674
+]
+- position: [
+  0.356730059515165,
+  0.33969153389651674
+]