Captures 50+ kernel launches as 3 CUDA Graphs (pre-fill, post-fill,
replay-step) for single-launch replay. Eliminates ~300μs/step of
CPU launch overhead at b=16.
Key challenges: device-resident step counter (no scalar arg changes
in graph), lobsim fill breaks the graph (split into pre/post),
ISV write ordering. Estimated 1.5-3× throughput improvement.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>