Raw CSC factor path streaming into helper shared memory

[krystophny]

Adds a raw CSC overload to sparse_factor — sparse_factor(solver, nrow, ncol, nz, col_ptr, row_idx, val, status) — that streams the matrix arrays straight into the UMFPACK helper's shared mapping instead of routing through a csc_t copy. Callers that already hold CSC arrays (NEO-2's sparse_solve_fortsparse adapter) drop one matrix-sized allocation per factorization.

Motivation: itpplasma/NEO-2#101's run-golden-record job dies on the runner during the multispecies QL case; local PSS profiling of that case shows the IPC backend peaking ~2 GB above the in-process UMFPACK path, with the adapter's csc_t copy the largest avoidable share.

Verification

Test fails on main

test_fortsparse_umfpack_ipc extensions (raw-factor roundtrip real/complex, refactor-after-free) do not exist on main; with the test but no raw overload the build fails to resolve the new sparse_factor specifics.

Test passes after fix

$ ctest --test-dir build --output-on-failure
 9/10 Test  #9: test_fortsparse_umfpack_ipc ......   Passed    0.13 sec
100% tests passed, 0 tests failed out of 10

fo lint clean (0 warnings).