feat(fxt): enhance watch TUI with full training metrics and gRPC helpers
- Add connect_channel/connect_channel_lazy with TLS auto-detection
- Expand TrainingSession to 35+ proto fields (RL diagnostics, hyperopt,
eval metrics, health counters, checkpoints)
- Add RL-specific rendering (entropy, action diversity, Q-values, rewards)
- Add hyperopt progress panel (trial/best objective tracking)
- Refactor all commands to use shared connect_channel helper
- Default API gateway URL to https://api.fxhnt.ai
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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