Use configured train device

AGENTS.md

@@ -93,13 +93,13 @@ Useful train controls:
 
 - `--resume`: resume from `<checkpoint-dir>/latest.pt`.
 - `--resume PATH`: resume from a specific checkpoint.
-- `--device DEVICE`: override the trainer device for this invocation.
 - `--set PATH=VALUE`: override config fields. It is repeatable and parses
   values as YAML, e.g. `--set traversal.num_workers=4` or
   `--set run.max_hours=null`.
 
 Common `--set` overrides:
 
+- `--set run.device=cuda`: set the trainer device.
 - `--set checkpoint.exact_resume=true`: require checkpoint config compatibility.
 - `--set checkpoint.save_latest=false --set checkpoint.save_every_iteration=false
   --set checkpoint.save_iteration_interval=0`: disable checkpoint writes.

src/coolrl_lost_cities/games/classic/deep_cfr/cli.py

@@ -105,7 +105,7 @@ def train_command(args: argparse.Namespace) -> None:
     trainer = DeepCFRTrainer(
         config,
         config.rules.to_lost_cities_config(seed=config.run.seed),
-        device=args.device or config.run.device,
+        device=config.run.device,
         extra_trackers=extra_trackers or None,
     )
     if resume_path:
@@ -204,7 +204,6 @@ def main(argv: list[str] | None = None) -> None:
     train = subparsers.add_parser("train")
     train.add_argument("--config")
     train.add_argument("--resume", nargs="?", const=_RESUME_LATEST, default=None)
-    train.add_argument("--device")
     train.add_argument(
         "--set",
         action="append",