Allow teams to use global executors by default

If someone has configured a team, but has not added any executors to it,
allow the team to then use the default global executor (which we enforce
must exist). This was always possible but previously had to be
configured directly in the tasks/dags, now it will be used by default.

Author: o-nikolas

airflow-core/src/airflow/jobs/scheduler_job_runner.py

@@ -2935,6 +2935,10 @@ def _try_to_load_executor(self, ti: TaskInstance, session, team_name=NOTSET) ->
                     # First executor that resolves should be the default for that team
                     if _executor.team_name == team_name:
                         executor = _executor
+                        break
+                else:
+                    # No executor found for that team, fall back to global default
+                    executor = self.job.executor
         else:
             # An executor is specified on the TaskInstance (as a str), so we need to find it in the list of executors
             for _executor in self.job.executors:

airflow-core/tests/unit/jobs/test_scheduler_job.py

@@ -7570,6 +7570,38 @@ def test_multi_team_try_to_load_executor_no_explicit_executor_with_team(
         # Should return the team-specific default executor set above
         assert result == mock_executors[1]
 
+    @conf_vars({("core", "multi_team"): "true"})
+    def test_multi_team_try_to_load_executor_no_explicit_executor_with_team_no_team_default(
+        self, dag_maker, mock_executors, session
+    ):
+        """Test executor selection when no explicit executor but team exists and team has no executors (should
+        fallback to the global executor)."""
+        clear_db_teams()
+        clear_db_dag_bundles()
+
+        team = Team(name="team_a")
+        session.add(team)
+        session.flush()
+
+        bundle = DagBundleModel(name="bundle_a")
+        bundle.teams.append(team)
+        session.add(bundle)
+        session.flush()
+
+        with dag_maker(dag_id="dag_a", bundle_name="bundle_a", session=session):
+            task = EmptyOperator(task_id="test_task")  # No explicit executor
+
+        dr = dag_maker.create_dagrun()
+        ti = dr.get_task_instance(task.task_id, session)
+
+        scheduler_job = Job()
+        self.job_runner = SchedulerJobRunner(job=scheduler_job)
+
+        result = self.job_runner._try_to_load_executor(ti, session)
+
+        # Should return the team-specific default executor set above
+        assert result == mock_executors[0]
+
     @conf_vars({("core", "multi_team"): "true"})
     def test_multi_team_try_to_load_executor_explicit_executor_matches_team(
         self, dag_maker, mock_executors, session