feat(studio): R3 step_respond、运行页 UX 与 R4 思考流式

新增 worldbook 步骤 LLM 回复（thinking/draft/questions/evaluation），
运行页聊天区与产物/选项联动；评价区标签改为「评价与修改建议」；
流式开关开启时 NDJSON 推送思考内容，完成后拆分更新各字段。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/api/routes/studioRoute.py

@@ -1,13 +1,16 @@
+import json
 import logging
 from typing import Any, Dict, List
 
 from fastapi import APIRouter, HTTPException
+from fastapi.responses import StreamingResponse
 
 from models.studio_models import (
     AdvanceRunRequest,
     CreateStudioProjectRequest,
     PipelineDefinition,
     RenameRunRequest,
+    RunMessageRequest,
     StudioProject,
     StudioProjectSummary,
     StudioRun,
@@ -186,6 +189,66 @@ async def advance_studio_run(
         raise HTTPException(status_code=500, detail=str(e))
 
 
+@router.post("/projects/{project_id}/runs/{run_id}/message")
+async def send_studio_run_message(
+    project_id: str, run_id: str, req: RunMessageRequest
+):
+    if req.stream:
+        async def ndjson_stream():
+            try:
+                async for event in studio_run_service.send_run_message_stream(
+                    project_id,
+                    run_id,
+                    req.content,
+                    profile_id=req.profileId,
+                    api_config=req.apiConfig,
+                ):
+                    yield json.dumps(event, ensure_ascii=False) + "\n"
+            except FileNotFoundError as e:
+                yield json.dumps(
+                    {"type": "error", "detail": str(e)}, ensure_ascii=False
+                ) + "\n"
+            except ValueError as e:
+                yield json.dumps(
+                    {"type": "error", "detail": str(e)}, ensure_ascii=False
+                ) + "\n"
+            except Exception as e:
+                logger.error(
+                    "Failed to stream studio run message %s/%s: %s",
+                    project_id,
+                    run_id,
+                    e,
+                )
+                yield json.dumps(
+                    {"type": "error", "detail": f"消息处理失败：{e}"},
+                    ensure_ascii=False,
+                ) + "\n"
+
+        return StreamingResponse(
+            ndjson_stream(),
+            media_type="application/x-ndjson",
+        )
+
+    try:
+        return await studio_run_service.send_run_message(
+            project_id,
+            run_id,
+            req.content,
+            stream=req.stream,
+            profile_id=req.profileId,
+            api_config=req.apiConfig,
+        )
+    except FileNotFoundError as e:
+        raise HTTPException(status_code=404, detail=str(e))
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
+    except Exception as e:
+        logger.error(
+            "Failed to send studio run message %s/%s: %s", project_id, run_id, e
+        )
+        raise HTTPException(status_code=500, detail=f"消息处理失败：{e}")
+
+
 @router.delete("/projects/{project_id}/runs/{run_id}")
 async def delete_studio_run(project_id: str, run_id: str):
     try: