Add analyze_fit_return_risk — Robert Engine return probability (api/fit_engine.py)

[Copilot]

Implements the Robert Engine physics formula that estimates return risk from fabric elasticity/recovery and the user's shoulder width, returning a risk percentage and size recommendation.

Changes

• api/fit_engine.py (new)

  • UserAnchors dataclass — biometric anchor point (shoulder width in cm)
  • Named constants replace magic numbers (_SHOULDER_MULTIPLIER, _TENSION_WEIGHT, _MAX_RETURN_RISK, _RISK_THRESHOLD, _PERCENTAGE_DIVISOR)
  • analyze_fit_return_risk(fabric, user_anchors, garment_id) — raises ValueError on elasticityPct ≤ 0 to prevent division-by-zero; caps risk at 95 %

• tests/test_fit_engine.py (new) — 10 unittest cases covering low/high risk paths, 95 % cap, exact 30 % boundary, response structure, rounding, and invalid-input guards

Usage

from api.fit_engine import UserAnchors, analyze_fit_return_risk

fabric = {"elasticityPct": 10.0, "recoveryPct": 20.0}
anchors = UserAnchors(shoulder_w=60.0)

result = analyze_fit_return_risk(fabric, anchors, "V10-BALMAIN-WHITE-SNAP")
# {
#   "garment_id": "V10-BALMAIN-WHITE-SNAP",
#   "return_risk_pct": 95.0,
#   "recommendation": "Sugerir Talla Superior"
# }

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Project	Deployment	Actions	Updated (UTC)
tryonyou-pilot	Error		Apr 7, 2026 1:43pm