Implemented neutral-sector core: extraction and validation
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Validation checks (manuscript table):
  field / type               : real (max|Im| = 0.00e+00), orthogonal
  unitarity residual         : 1.33e-15
  uniform-vector eigenvalue  : 1.000000+0.000000i
  det R_N                    : -1.000000
  eigenphases (deg)          : [-166.8246  -43.3737  -15.2835    0.       15.2835   43.3737  166.8246
  180.    ]
  depth-2 reconstruction res. : 1.11e-15
  depth-3 reconstruction res. : 1.50e-15

The nominal gate parameters of Ref. [washburn2026] (theta=pi/4, psi=2pi/3)
define a complex operator that assigns the uniform vector eigenvalue e^{i pi/2}=i;
the implemented operator above is real, fixes the uniform vector with eigenvalue +1,
and is the archived representative used to exercise the neutral sector.
