Python: Add CreateConversationExecutor, fix input routing, remove unused handler layer (#4159)

* Fixed declarative deep research sample

* Small fix

* Resolved comment

* Add CreateConversationExecutor, fix input routing, remove unused handler layer

* Address Copilot feedback

* Fix System.ConversationId

---------

Co-authored-by: Dmytro Struk <13853051+dmytrostruk@users.noreply.github.com>

python/packages/declarative/tests/test_workflow_state.py

@@ -223,3 +223,33 @@ class TestWorkflowStateResetTurn:
 
         assert state.get("Workflow.Inputs.query") == "test"
         assert state.get("Workflow.Outputs.result") == "done"
+
+
+class TestWorkflowStateConversationIdInit:
+    """Tests that WorkflowState generates a real UUID for System.ConversationId."""
+
+    def test_conversation_id_is_not_default(self):
+        """System.ConversationId should be a UUID, not 'default'."""
+        import uuid
+
+        state = WorkflowState()
+        conv_id = state.get("System.ConversationId")
+        assert conv_id is not None
+        assert conv_id != "default"
+        uuid.UUID(conv_id)  # Raises ValueError if not a valid UUID
+
+    def test_conversations_dict_initialized(self):
+        """System.conversations should contain an entry matching ConversationId."""
+        state = WorkflowState()
+        conv_id = state.get("System.ConversationId")
+        conversations = state.get("System.conversations")
+        assert conversations is not None
+        assert conv_id in conversations
+        assert conversations[conv_id]["id"] == conv_id
+        assert conversations[conv_id]["messages"] == []
+
+    def test_each_instance_generates_unique_id(self):
+        """Each WorkflowState instance should have a different ConversationId."""
+        state1 = WorkflowState()
+        state2 = WorkflowState()
+        assert state1.get("System.ConversationId") != state2.get("System.ConversationId")