CZTargetGateset: PhysicalZ op gets decomposed when additional_gates contains a PhysicalZ GateFamily

[verult]

Description of the issue

Expected cirq.Z to not decompose into cirq.PhasedXZGate in the code snippet below (probably the same issue in other target gatesets as well):

How to reproduce the issue

>>> cirq.optimize_for_target_gateset(
...     cirq.Circuit(cirq.Z(cirq.LineQubit(0)).with_tags(cg.PhysicalZTag())),
...     gateset=cirq.CZTargetGateset(additional_gates=[cirq.GateFamily(cirq.ZPowGate, tags_to_accept=[cg.PhysicalZTag()])])
... )
cirq.Circuit([
    cirq.Moment(
        cirq.PhasedXZGate(axis_phase_exponent=0.0, x_exponent=0.0, z_exponent=1.0).on(cirq.LineQubit(0)),
    ),
])

Are we checking only the gate and not the operation when decomposing?

@tanujkhattar

[verult]

My bad, the example given above isn't an issue because CZTargetGateset ejects Paulis as expected. The actual code that failed was this:

cirq.optimize_for_target_gateset(
     cirq.Circuit(
                cirq.Z(_qa).with_tags(cirq_google.PhysicalZTag()) ** 0.5, cirq.CZ(_qa, _qb)
     ),
     gateset=cirq.CZTargetGateset(additional_gates=[cirq.GateFamily(cirq.ZPowGate, tags_to_accept=[cg.PhysicalZTag()])])
)

This fails because raising the whole operation to an exponent removes all tags, which is a separate issue but not related to target gatesets.