Drop the netlib QUADPACK and SLATEC dependencies (Z3)

[krystophny]

Drop the netlib QUADPACK and SLATEC dependencies (Z3)

Removes the vendored netlib QUADPACK and SLATEC sources now that fortnum supplies the quadrature, special functions, roots, and ODE kernels. Cumulative tip of the migration stack; fortnum pinned to main 974dcf1.

This branch carries every kernel migration (k1..k8), both region-root and equilibrium ODE rewires (z1, z2), the golden-record CI timeout fix (#140), and the uniform fortnum pin.

Stack reconciliation

The branches were rebuilt as a strictly linear cumulative chain on main 428a708:

k1 (+ golden CI fix) -> k2 -> k3 -> k4 -> k5 -> k6 -> k7 -> k8 -> z1 -> z2 -> z3

Each branch's tree equals its prior content plus its own increment, every branch pins fortnum to 974dcf1, z2 carries the ddeabm equilibrium rewire, k4 carries the KiLCA DOP853 swap.

Verification

Cumulative tip golden against the main reference (uv venv: pytest numpy scipy h5py f90nml matplotlib; golden from main 428a708; bar rtol=1e-8 atol=1e-15, unchanged, stored golden not regenerated):

RESULT: 16/114 pass, 98 fail
worst rel=3.850e+00 abs=4.194e+06
fails: dqle*/dqli* (Fokker-Planck conductivity), Br* (fields), T_EM_phi_*, a few Te/Ti/n/Er

The tip does not pass. Bisection over the stack:

k1 special funcs      114/114  worst 0
k2 QUADPACK           114/114  worst 0
k3 KiLCA quadrature   114/114  worst 0
k4 KiLCA ODE           16/114  worst rel 3.85   <- regression enters here

The single blocker is the KiLCA background equilibrium ODE on #143 k4: DOP853 does not reproduce the GSL rk8pd golden to 1e-8 at a near-resonant grid point (method residual about 4e-7, amplified by the iterative balance solve). Details and the fortnum re-entrant ddeabm C ABI needed to match GSL are in #143. Every other kernel and ODE site reproduces main exactly.

Merge order

#140 -> #141 -> #142 -> #143 -> #144 -> #145 -> #146 -> #147 -> #148 -> #149 -> #150.

Note: fortnum pin updated to current main (92de6e9) after a fortnum history rewrite; old shas no longer resolve.