Fix W&B run reuse across ART models (#618)

* Fix wandb run reuse across models

* Remove ART wandb regression test

Author: Kovbo

src/art/model.py

@@ -470,6 +470,7 @@ def _get_wandb_run(self) -> Optional["Run"]:
                 id=self.name,
                 config=self._wandb_config or None,
                 resume="allow",
+                reinit="create_new",
                 settings=wandb.Settings(
                     x_stats_open_metrics_endpoints={
                         "vllm": "http://localhost:8000/metrics",
@@ -492,18 +493,18 @@ def _get_wandb_run(self) -> Optional["Run"]:
 
             # Define training_step as the x-axis for all metrics.
             # This allows out-of-order logging (e.g., async validation for previous steps).
-            wandb.define_metric("training_step")
-            wandb.define_metric("time/wall_clock_sec")
-            wandb.define_metric("reward/*", step_metric="training_step")
-            wandb.define_metric("loss/*", step_metric="training_step")
-            wandb.define_metric("throughput/*", step_metric="training_step")
-            wandb.define_metric("costs/*", step_metric="training_step")
-            wandb.define_metric("time/*", step_metric="training_step")
-            wandb.define_metric("data/*", step_metric="training_step")
-            wandb.define_metric("train/*", step_metric="training_step")
-            wandb.define_metric("val/*", step_metric="training_step")
-            wandb.define_metric("test/*", step_metric="training_step")
-            wandb.define_metric("discarded/*", step_metric="training_step")
+            run.define_metric("training_step")
+            run.define_metric("time/wall_clock_sec")
+            run.define_metric("reward/*", step_metric="training_step")
+            run.define_metric("loss/*", step_metric="training_step")
+            run.define_metric("throughput/*", step_metric="training_step")
+            run.define_metric("costs/*", step_metric="training_step")
+            run.define_metric("time/*", step_metric="training_step")
+            run.define_metric("data/*", step_metric="training_step")
+            run.define_metric("train/*", step_metric="training_step")
+            run.define_metric("val/*", step_metric="training_step")
+            run.define_metric("test/*", step_metric="training_step")
+            run.define_metric("discarded/*", step_metric="training_step")
             self._sync_wandb_config(run)
         return self._wandb_run
 
@@ -562,14 +563,16 @@ def _log_metrics(
                 run.log(prefixed)
 
     def _define_wandb_step_metrics(self, keys: Iterable[str]) -> None:
-        import wandb
+        run = self._wandb_run
+        if run is None or run._is_finished:
+            return
 
         for key in keys:
             if not key.startswith("costs/"):
                 continue
             if key in self._wandb_defined_metrics:
                 continue
-            wandb.define_metric(key, step_metric="training_step")
+            run.define_metric(key, step_metric="training_step")
             self._wandb_defined_metrics.add(key)
 
     def _route_metrics_and_collect_non_costs(