Add direct EQDSK equilibrium and perturbation-field inputs

[krystophny]

Summary

• add direct axisymmetric GEQDSK input (inp_swi=11) in native geometric coordinates
• add direct complex R-Z perturbation input (inp_swi_pert=11)
• retain independent switches for the supported Boozer chartmap + .bc path
• reject mixed direct/Boozer coordinate charts deterministically
• preserve signed GEQDSK pitch, flux, Jacobian, and field-line-label drift projection

Scope cleanup

The branch is one focused direct-field commit. Formerly bundled converters, signed POTATO modes, zero-rotation handling, and bracketing are separate PRs #102, #105, #104, and #103. The pre-existing Boozer Fourier and POTATO representation fixes are #106 and #107.

Validation

• full cumulative fo pipeline passes
• independent GEQDSK pitch/Jacobian/flux and R-Z perturbation tests pass
• legacy Boozer behavior is bit-for-bit identical to main at four ITER TC24 surfaces with both old and canonical profile/plasma inputs

Stack: #104 -> this PR. This PR itself does not alter the Boozer/Boozer production path.

[krystophny]

Reviewed latest 1e0b622d. This is now the bounded direct-field core: independent equilibrium/perturbation switches, native EQDSK field use, geometric toroidal phase mapping, and validated root-domain limits. Current main is an ancestor. The integrated stack passes the complete fo pipeline; no curve-selected sign or phase is introduced. No blocking finding.