optimal_n_episodes() returns 8192 on H100 (132 SMs) but the GPU
experience collector pre-allocates buffers for MAX_EPISODES_LIMIT=4096.
Exceeding that caused "Episode count exceeds allocated buffer size"
and silent fallback to CPU. Now all 3 auto-scaling sites clamp at 4096.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>