Add store_transpose: store transposed feedbacks alongside normal feedbacks, expose evaluate_transpose

[Copilot]

When generating C code, it's useful to have feedbacks stored in transposed layout (solutions in the inner/contiguous index) for SIMD-friendly evaluation — but the normal layout must still be present since evaluate uses it. This PR stores both arrays and adds a dedicated evaluate_transpose function.

Changes

• codegen always writes pdaqp_feedbacks (normal layout: parameters in inner index)
• When store_transpose=true, also writes pdaqp_feedbacks_T (transposed: solutions in inner index) alongside the normal array
• evaluate is unchanged — always uses pdaqp_feedbacks
• evaluate_transpose is generated when store_transpose=true; uses outer-parameter / inner-solution loop over pdaqp_feedbacks_T; applies output clipping consistently with evaluate
• Header declares evaluate_transpose only when store_transpose=true

Usage

# Both pdaqp_feedbacks and pdaqp_feedbacks_T written; both evaluate and evaluate_transpose generated
codegen(sol; dir="out", store_transpose=true)

Generated C:

// Normal evaluate — row-major feedbacks, outer loop over solutions
void pdaqp_evaluate(c_float* parameter, c_float* solution);

// Transposed evaluate — solutions contiguous in memory, outer loop over parameters
void pdaqp_evaluate_transpose(c_float* parameter, c_float* solution);