feat: two-phase hyperopt + backtest evaluator VRAM leak fix
Two-phase hyperopt splits 31D PSO search into sequential phases:
- Phase 1 (--phase fast, default): fix architecture to small network
(hidden_dim=128, num_atoms=11), search learning dynamics (~15D).
- Phase 2 (--phase full): fix dynamics from Phase 1 JSON, search
architecture (~5D). Halves dimensionality per phase → better convergence.
- Phase 1 output includes best_continuous_vector for Phase 2 consumption.
GpuBacktestEvaluator Drop impl: sync forked stream, destroy CUDA graph
and cuBLAS handles before CudaSlice buffers drop. Fixes 261MB/trial
VRAM leak on H100 hyperopt.
ml-core clippy fixes: hex literal, remove dead check_err drain,
unnecessary safety comment, unused OnceLock import.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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