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/アナル/part.yaml

@@ -0,0 +1,81 @@
+id: アナル
+original_key: アナル
+resource: カーソル
+morph_x: 1
+morph_y: 5
+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
+- x: 0
+  y: 4
+  file: x0y4.svg
+fields:
+- name: ヘッド
+- name: ユニット
+joints:
+- position: [
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+  0.11355214938035088
+]
+- position: [
+  0.015096514070287394,
+  0.008994956633415117
+]
+- position: [
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+]
+- position: [
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+  0.024174770409468336
+]
+- position: [
+  0.012973415475779428,
+  0.011724460486568064
+]
+- position: [
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+  0.016050552809990976
+]
+- position: [
+  0.01659846530546976,
+  0.01202250245401227
+]
+- position: [
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+  0.015096514070287394
+]
+- position: [
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+  0.011361187233872302
+]
+- position: [
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+  0.010079949052140581
+]
+- position: [
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+  0.11928408161324774
+]
+- position: [
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+  0.12654698894011573
+]
+- position: [
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+  0.1353153973823115
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+- position: [
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+]