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/胸郭肌/part.yaml

@@ -0,0 +1,91 @@
+id: 胸郭肌
+original_key: 胸郭肌
+resource: 胴体
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 甲殻
+- name: 淫タトゥ
+- name: 悪タトゥ
+- name: 植タトゥ
+- name: 隈取
+- name: 鱗
+- name: 蜘蛛
+- name: コア
+joints:
+- position: [
+  0.030891347660494964,
+  0.01987651837749724
+]
+- position: [
+  0.03726900647515902,
+  0.01987651837749724
+]
+- position: [
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+  0.008105469171541388
+]
+- position: [
+  0.09500000000000001,
+  0.08549960227557413
+]
+- position: [
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+  0.002410254333550322
+]
+- position: [
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+  0.017744520306784285
+]
+- position: [
+  0.04539696726208402,
+  0.03455415935059752
+]
+- position: [
+  0.04628576764408492,
+  0.03574926764201532
+]
+- position: [
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+  0.033579071236846815
+]
+- 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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+  0.03487417433351471
+]
+- position: [
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+  0.03699551367359685
+]
+- position: [
+  0.05238638987595082,
+  0.07117155997149677
+]
+- position: [
+  0.05572767786649241,
+  0.0748626904232397
+]