feat: 新增追问模式和iOS本地化，重构后端输出模型

backend/src/core/agentscope/runtime/runner.py

@@ -55,7 +55,7 @@ from core.agentscope.runtime.protocols import PipelineLike
 @dataclass(frozen=True)
 class StageExecutionResult:
     message: Msg
-    payload: dict[str, Any]
+    validated_output: WorkerAgentOutputLite | FollowUpOutput
     response_metadata: dict[str, Any]
 
 
@@ -242,7 +242,7 @@ class AgentScopeRunner:
             derived_divination=derived_divination,
             language=language,
         )
-        worker_output = worker_output_model.model_validate(worker_result.payload)
+        worker_output = worker_result.validated_output
         await self._emit_step_event(
             pipeline=pipeline,
             run_input=run_input,
@@ -284,9 +284,10 @@ class AgentScopeRunner:
             llm_config=stage_config.llm_config,
             tools=None,
             now_utc=datetime.now(timezone.utc),
+            runtime_mode=runtime_mode.value,
         )
 
-        _, worker_payload_raw = await finalize_json_response(
+        _, worker_payload = await finalize_json_response(
             model=tracking_model,
             formatter=formatter,
             base_messages=[Msg("system", system_prompt, "system"), *input_messages],
@@ -294,7 +295,6 @@ class AgentScopeRunner:
             retries=2,
             language=language,
         )
-        worker_payload = worker_output_model.model_validate(worker_payload_raw)
         response_metadata = self._llm_pricing_service.build_usage_metadata(
             model=stage_config.model_code,
             usage_summary=tracking_model.usage_summary(),
@@ -312,9 +312,8 @@ class AgentScopeRunner:
                 name=stage_config.agent_type.value,
                 role="assistant",
                 content=worker_payload.answer,
-                metadata=worker_payload.model_dump(mode="json", exclude_none=True),
             ),
-            payload=worker_payload.model_dump(mode="json", exclude_none=True),
+            validated_output=worker_payload,
             response_metadata=response_metadata,
         )
 
@@ -336,7 +335,7 @@ class AgentScopeRunner:
                 question=raw_user_text, language=language
             )
 
-        if derived_divination is not None and context_messages:
+        if context_messages:
             last = context_messages[-1]
             if last.role == "user":
                 context_messages[-1] = Msg(
@@ -346,11 +345,6 @@ class AgentScopeRunner:
                 )
                 return context_messages
 
-        if context_messages:
-            last = context_messages[-1]
-            if last.role == "user":
-                return context_messages
-
         user_msg = Msg(name="user", role="user", content=user_text)
         return [*context_messages, user_msg]