- Promote HEAD_DIM from module constant to constructor parameter - FmhaKernel(head_dim=64, s_k=128, ...) — default 64 for regression - All references to HEAD_DIM replaced with self.head_dim - PV MMA tiler, V layout, softmax corr_tiles all parameterized - TMEM budget warning when num_tmem_alloc_cols > 512 - New test: test_fmha_v3_stage_d1.py tests hd=64 (regression) and hd=512 - Stage C test preserved as-is for reference