petrol-fastwin-v5 (WBF + agreement gate)

Iteration of v3. Same two-detector WBF ensemble:

• weights/havengo.onnx — m50 0.901 / fp 0.884 (high recall)
• weights/superbit.onnx — m50 0.892 / fp 0.944 (high precision)

v5 change: cluster_size ≥ 2 — require both models to propose a box (within WBF IoU 0.55) for it to survive. v3 hurt the fp pillar by promoting singleton clusters (only one model agreed) into the output; this drops them structurally.

Per-model weights 0.45 / 0.55 favor SuperBit slightly.