Python: Remove warnings from workflow builder on not using factories (#2808)

* Revert concurrent

* Fix comments

python/packages/core/tests/workflow/test_concurrent.py

@@ -63,7 +63,7 @@ def test_concurrent_builder_rejects_duplicate_executors_from_factories() -> None
         return _FakeAgentExec("dup", "B")  # same executor id
 
     builder = ConcurrentBuilder().register_participants([create_dup1, create_dup2])
-    with pytest.raises(ValueError, match="Executor with ID 'dup' has already been created."):
+    with pytest.raises(ValueError, match="Duplicate executor ID 'dup' detected in workflow."):
         builder.build()
 
 

python/packages/core/tests/workflow/test_workflow_builder.py

@@ -497,7 +497,13 @@ def test_mixing_eager_and_lazy_initialization_error():
     builder.register_executor(lambda: MockExecutor(id="Lazy"), name="Lazy")
 
     # Mixing eager and lazy should raise an error during add_edge
-    with pytest.raises(ValueError, match="Both source and target must be either names"):
+    with pytest.raises(
+        ValueError,
+        match=(
+            r"Both source and target must be either registered factory names \(str\) "
+            r"or Executor/AgentProtocol instances\."
+        ),
+    ):
         builder.add_edge(eager_executor, "Lazy")