Fix complex GMRES inner products

[2002WYT]

Summary

Fix the complex-valued inner products used by device code and GMRES Arnoldi orthogonalization.

Fixes #377

Root cause

The device implementation of dotc(...) in src/blas.cu calls Cublas::dot(...).

For complex double precision, this maps to the unconjugated cublasZdotu, while dotc(x, y) is expected to compute the Hermitian inner product x^H y.

After restoring the correct dotc semantics, the GMRES Modified Gram-Schmidt projection also needs its arguments swapped. The current expression computes w^H v_k, whereas Arnoldi orthogonalization requires v_k^H w.

Changes

• Use Cublas::dotc(...) in the two device implementations of dotc(...).
• Change the GMRES projection argument order from dot(w, v_k) to dot(v_k, w).

Testing

Tested using the 3x3 complex reproducer from #377 with:

• AMGX mode: dZZI
• GMRES restart: 10
• No preconditioner
• Same matrix, RHS, initial guess, and solver configuration

Results:

	Original v2.5.0	Patched
Total iterations	500	3
Final residual	2.955383e-05	4.981581e-16
Status	Did not converge	Converged

The same reproducer was also tested after applying the patch to the current main branch.

Full reproduction details and logs are available in #377.