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/青筋左/part.yaml

@@ -0,0 +1,11 @@
+id: 青筋左
+original_key: 青筋左
+resource: 胴体
+morph_x: 1
+morph_y: 1
+variants:
+- x: 0
+  y: 0
+  file: x0y0.svg
+fields:
+- name: 血管

SlaveMatrix/Assets/Parts/青筋左/x0y0.svg

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1 1">
+<g transform="translate(0.3253358894007324,0.10604815195191086) rotate(0) scale(1,1) translate(-0.005607832739230754,-0.005607832739230756)"><path d="M -0.003292022660526815 -0.0060522946746772305 C -0.0030545819166830322 -0.005796452230757093 0.00019836707561553127 -0.0027354515899659488 -0.0004427337344014208 -0.0029821853476355745 C 0.00019836707561553127 -0.0027354515899659488 0.0048048471258497795 -0.0031005982688922327 0.00440118705967661 -0.0030914895826417207" fill="none" stroke="#000000" stroke-width="0.001"/>
+<path d="M 0.004645366431299705 -0.001384303342543258 C 0.004281037663732294 -0.0012762816594803763 -0.0002609347067868234 0.00036453319356138085 0.00027342122049076577 -8.8043145788678E-05 C -0.0002609347067868234 0.00036453319356138085 -0.0019369318557415425 0.004391167385944626 -0.001766904696031365 0.004046612729657449" fill="none" stroke="#000000" stroke-width="0.001"/>
+<path d="M -0.0032148008013176033 0.003466973430186155 C -0.0031445444794749094 0.0030958277467893532 -0.0024804266096356887 -0.0017056788621353522 -0.0023717249392052743 -0.0009867747705754645 C -0.0024804266096356887 -0.0017056788621353522 -0.0046981788387556855 -0.005507634076695584 -0.004519220846482577 -0.005159875668532498" fill="none" stroke="#000000" stroke-width="0.001"/>
+</g></svg>