Replaces eps-greedy + Boltzmann on direction with:
- Training: argmax of (sample_C51 + sample_IQN) per direction (Thompson)
- Eval: argmax of (E_C51 + E_IQN) per direction (no exploration)
Conviction calculation now reads e_dir[] (joint E[Q] computed inline)
preserving the spec's requirement that conviction uses raw E[Q] not
samples (avoids Kelly cap jitter).
Magnitude/order/urgency branches: unchanged.