train_run: a run that already has a gate verdict is not trained again without --force

The exit code 2 of a failed gate made the cycle script retry and train
2026-10-01_v4-recipeA twice.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tools/train_run.py

@@ -174,12 +174,18 @@ def main(argv=None) -> int:
     ap.add_argument("--baseline", default=None, help="gold report to gate against (default: the active model's)")
     ap.add_argument("--no-promote", action="store_true", help="gate, but leave production.json alone")
     ap.add_argument("--skip-train", action="store_true", help="reuse runs/<id>/ultralytics/train/weights/best.pt")
+    ap.add_argument("--force", action="store_true", help="train again a run that already has a gate verdict")
     ap.add_argument("--set", nargs="*", default=[], metavar="KEY=VALUE",
                     help="override any Ultralytics train argument, e.g. fliplr=0 mask_ratio=1 overlap_mask=true; recorded in the ledger")
     args = ap.parse_args(argv)
 
     run = ledger.load(args.run_id)
     run_dir = ledger.run_path(args.run_id).parent
+    # A gate verdict is an outcome, not a crash: the exit code 2 of a failed gate must not make a
+    # wrapper's retry train the whole run a second time (cycle 4 lost two hours that way).
+    if run.get("status") in ("gate_failed", "gate_passed", "promoted", "deployed") and not (args.skip_train or args.force):
+        print(f"{args.run_id} is already {run['status']}: not training it again (--force to retrain, --skip-train to re-measure)")
+        return 0
     ds = dataset_dir(run)
     data_yaml = resolved_yaml(run_dir, ds)
     names = [v for _, v in sorted(json.loads((ds / "source.json").read_text())["classes"].items(), key=lambda kv: int(kv[0]))] \