petrol-fastwin-v7 (TTA-flip + agreement gate, single 19.4 MB model)

Same agreement-gate pattern that drove v5's +12% composite, but the "second opinion" comes from the same model running on a horizontally-flipped image instead of a different model.

• one ONNX (SuperBitDev/petrol2 weights, 19.4 MB FP16)
• repo total ≤ 30 MB ✓ (fits the petrol element rule)
• run pass 1 on original, pass 2 on flipped, un-flip pass-2 boxes
• WBF cluster boxes within IoU 0.55, emit only where BOTH passes contributed
• singletons = noise = dropped