Adds the RobertEngineV10 class — the core fabric simulation engine for the TryOnYou virtual try-on experience — along with full test coverage.

api/robert_engine.py

• Pilot Collection (__init__): five Lafayette looks (eg0–eg4), each parameterised by drape, GSM, elasticity, recovery, and friction
• Module 1 — _calculate_physics: Lafayette factor (shoulder→garment width), gravity stretch (≤15% elongation scaled by GSM), and sinusoidal elasticity breathing
• Module 2 — _get_visual_effects: dynamic silk highlight when friction < 0.35, 3 or 5 fold-shadows driven by drape, and a golden scan-line for 0 < fit_score < 95
• Module 3 — get_accessory_render: body-anchored vs. floating-exhibition bag at fixed alpha 0.88
• Module 4 — process_frame: full pipeline returning a render buffer with patent-stamped metadata (PCT/EP2025/067317); unknown look_id falls back to eg0

engine = RobertEngineV10()
result = engine.process_frame(
    look_id="eg0", shoulder_w=450, hip_y=900,
    fit_score=88, canvas_dim={"w": 1080, "h": 1920}
)
# result["render"]   → {"width": ..., "height": ..., "effects": {"highlight": ..., "folds": [...], "scan_line_y": ...}}
# result["metadata"] → {"patent": "PCT/EP2025/067317", "claim": "22_PROTECTED", "recovery_status": "STABLE"}

tests/test_robert_engine.py

37 unittest cases across 5 test classes — physics boundary conditions (GSM clamping, breathing oscillation), visual-effect rules (fold count, highlight threshold, scan-line bounds), accessory scaling, and full-pipeline metadata assertions.