GCC 15 (Fedora 43, the cuda-13.0 runner base) diagnoses errors in
uninstantiated template bodies, tripping over a latent typo
(set_slice3x3) in the CUTLASS matrix.h pulled in by mistralrs-quant's
cutlass_moe kernels. The offending Matrix::rotation/reflection members
are never instantiated, so defer the diagnosis via NVCC_APPEND_FLAGS
(read directly by nvcc) instead of failing every build/flavour.
Also reduce the upstream poll cron from 6h to 1h for quicker feedback;
the in-flight guard already prevents re-dispatch over a running build.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>