feat: 完善会商产物提交匹配与流式写文件预览

席位流程图按已提交 Markdown 对齐；流式未命名产物不再误请求 artifacts API，并兼容临时文件名路径。同时补强会话流中断识别与 8BF/岗位会商展示。

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

offline-backend-20260512/backend/app/gateway/routers/artifacts.py

@@ -36,6 +36,27 @@ EDITABLE_TEXT_SUFFIXES = {
     ".log",
 }
 
+_VIRTUAL_USER_DATA_PREFIX = "mnt/user-data"
+
+
+def coerce_artifact_virtual_path(path: str) -> str:
+    """Normalize an artifacts URL path to a sandbox virtual path.
+
+    Streaming write previews may request a bare filename such as
+    ``未命名文件.md`` before the model has emitted a real
+    ``/mnt/user-data/outputs/...`` path. Mapping a single path segment into
+    the thread outputs directory turns that into a normal 404 (file not written
+    yet) instead of HTTP 400 ``Path must start with /mnt/user-data``.
+    """
+    stripped = path.strip().lstrip("/").replace("\\", "/")
+    if not stripped:
+        raise HTTPException(status_code=400, detail="Path must start with /mnt/user-data")
+    if stripped == _VIRTUAL_USER_DATA_PREFIX or stripped.startswith(_VIRTUAL_USER_DATA_PREFIX + "/"):
+        return stripped
+    if "/" in stripped or stripped in {".", ".."}:
+        raise HTTPException(status_code=400, detail="Path must start with /mnt/user-data")
+    return f"{_VIRTUAL_USER_DATA_PREFIX}/outputs/{stripped}"
+
 
 class ArtifactUpdateRequest(BaseModel):
     content: str
@@ -198,6 +219,7 @@ async def get_artifact(thread_id: str, path: str, request: Request, download: bo
         - Download file: `/api/threads/abc123/artifacts/mnt/user-data/outputs/data.csv?download=true`
         - Active web content such as `.html`, `.xhtml`, and `.svg` artifacts is always downloaded
     """
+    path = coerce_artifact_virtual_path(path)
     # Check if this is a request for a file inside a .skill archive (e.g., xxx.skill/SKILL.md)
     if ".skill/" in path:
         # Split the path at ".skill/" to get the ZIP file path and internal path
@@ -285,6 +307,7 @@ async def update_artifact(
     if ".skill/" in path:
         raise HTTPException(status_code=400, detail="Skill archive contents are read-only.")
 
+    path = coerce_artifact_virtual_path(path)
     actual_path = await aresolve_thread_virtual_path(thread_id, path)
     logger.info(f"Updating artifact path: thread_id={thread_id}, requested_path={path}, actual_path={actual_path}")