Validate coherence-preserving extraction across the full native path

Validate that the implemented parity-extraction circuits preserve the required within-sector coherence across the full 15-qubit native path, including the query exhibiting a repeated sign reversal.

Background

The native-device implementation tests parity extraction on a 15-qubit path under a detector model that requires coherence preservation within parity sectors. A coherence diagnostic produced an unexplained sign reversal for one query, and a focused follow-up reproduced the reversal for both encoded bits and both witness phases. Consequently, the hardware evidence does not yet validate the detector contract across the entire path.

Resolving this issue requires diagnosing the affected extraction circuit and repeating the coherence tests with broader sector and phase coverage before attributing any allocation-performance comparison to a coherence-preserving physical service.