[KIM] Complete the Phi/Br integral ion transport tensor

[krystophny]

What to build

Extend the verified Phi-only tracer bullet to the complete ion transport tensor for the Phi and radial-magnetic-drive channels. Periodic KIM must return D11, D12, D21, and D22 after contracting every ordered Phi/Br field pair over the configured cyclotron harmonics.

This slice must preserve the quadratic-form structure instead of porting the legacy local formula.

Acceptance criteria

• All four tensor entries include Phi-Phi, Phi-Br, Br-Phi, and Br-Br contributions.
• Every coefficient-polynomial family used by these channels is checked against the Mathematica oracle.
• Each ordered field-pair channel can be activated independently and matches a direct reference contraction.
• The quadratic form is explicitly Hermitianized before its real part is returned.
• D12 and D21 satisfy the derived Onsager tolerance.
• The symmetric transport tensor is positive semidefinite within documented numerical tolerance for admissible fixtures.
• A common complex phase rotation of Phi and Br leaves the tensor invariant.
• Harmonic and Fourier-grid convergence tests cover a finite-FLR ion case.
• All four entries recover the established drift-kinetic ion tensor in the documented zero-FLR, ell=0, local diagonal limit.

Blocked by

• [KIM] Deliver a Phi-only integral-ion D11 tracer bullet #286