Convert Device::Cpu fallback patterns to hard errors across all
hyperopt adapters and the Mamba2 trainer. On H100, CUDA must be
available — silent CPU fallback runs at 1/10th throughput.
Models hardened: TFT, Mamba2, TGGN, TLOB, Liquid, KAN, xLSTM,
Diffusion, ContinuousPPO (hyperopt adapters) + Mamba2 (trainer).
Pattern: Device::new_cuda(0).unwrap_or_else(|e| { warn!(...); Cpu })
→ Device::new_cuda(0).map_err(|e| MLError::ConfigError(...))?
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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