Release 0.7.2

SOLVAX 0.7.2 adds block_thomas_factor_fn, the generated full-factor path for repeated primal and transpose block-tridiagonal solves. Each callback block is assembled exactly once. The factorization retains the required Schur LU and off-diagonal state without also materializing a complete diagonal input band.

Tests cover one and multiple right-hand sides, one-block and multi-block systems, exact transpose reuse, float32, float64, jax.jit, reverse-mode differentiation, and runtime callback counts. This patch is the minimum SOLVAX version required by NTX’s generated-factor custom-VJP integration.