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/虫鎌/part.yaml

@@ -0,0 +1,86 @@
+id: 虫鎌
+original_key: 虫鎌
+resource: 肢左
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 虫鎌節
+- name: 虫棘1
+- name: 虫棘2
+- name: 虫棘3
+- name: 虫棘4
+- name: 虫鎌1
+- name: 虫鎌2
+- name: 虫鎌3
+- name: 虫孔1
+- name: 虫孔2
+- name: 輪
+joints:
+- position: [
+  0.040429841782210346,
+  0.04112622562174576
+]
+- position: [
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+  0.09576671578447664
+]
+- position: [
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+]
+- position: [
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+]
+- position: [
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+  0.10058650533665284
+]
+- position: [
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+  0.09802160550018327
+]
+- position: [
+  0.08939969953595228,
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+]
+- position: [
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+]
+- position: [
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+]
+- position: [
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+- position: [
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+- position: [
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+- position: [
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+  -0.0022810158830894735
+]
+- position: [
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+- position: [
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+  0.011300670369192287
+]
+- position: [
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+  0.004215979623981122
+]