132cd5b950
Pre-compute all FM discriminator outputs using demod_fm_with_prev which processes 8 samples at a time via AVX2 atan2, then iterate the scalar results through the rest of the stereo pipeline. Eliminates per-sample f32::atan2 calls from the inner loop. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> Signed-off-by: Stan Grams <sjg@haxx.space>