Ran scripts/bench_optimizations.py unmodified across three machines + an
engine-level tiled×compile extension with ground-truth alpha scoring.
Headlines: sdpa = 4.5x regression on M1 at 2048 (bf16 innocent — isolated
per-toggle on both Ultras); stage_gc harmful on Ultra-class; tiled 768/64
+ compile = best 2048 config on both Ultras; 24GB Macs swap-bound at 2048
full-frame (tiled required).
