feat(assets): face-based segmentation pipeline + solidify for hair/clothing

Segmentation:
- Face-based exclusive assignment (no overlap, no caps needed)
- Hips split from torso (pelvis as own segment)
- Torso_upper independent (spine_03 + clavicle, not a variant)
- Clavicle moved from arm_upper to torso_upper

Hair pipeline:
- Solidify modifier (20mm) for scalp hair volume
- Normal recalculation before solidify for consistent direction
- Eyebrows/facial hair NOT solidified
- Fixed mask generation (was outputting black, now white)

Clothing pipeline:
- Solidify modifier (25mm) for clothing thickness
- Peasant shoes added from Fantasy pack

Tooling:
- convert_outfit.py with solidify support
- inspect_glb.py, check_hair_symmetry.py for debugging
- Segment reference distribution locked
- Q-063 footsteps VFX filed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

decisions/questions-architecture.md

@@ -101,4 +101,11 @@ Technical foundation questions: engine, protocols, data structures, performance,
 
 ---
 
-*14 questions (7 resolved, 1 partially resolved, 6 open). Last updated: 2026-03-19.*
+### Q-063: Footstep VFX system (Godot Asset Library #4122)
+- **Status:** Open
+- **Question:** Integrate the Footsteps asset (https://godotengine.org/asset-library/asset/4122) into the character visual system. Jeroen wants this in the game. Evaluate: how does it hook into the animation system? Does it work with our toon shader pipeline? Should footstep triggers be animation events or raycast-based?
+- **Cross-reference:** D-149 (3D characters rendered live), D-160 (body segments)
+
+---
+
+*15 questions (7 resolved, 1 partially resolved, 7 open). Last updated: 2026-03-22.*