[Chore/Refactor] Improve type checking configuration (#25185)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/core/plugin/utils/chunk_merger.py

@@ -1,6 +1,6 @@
 from collections.abc import Generator
 from dataclasses import dataclass, field
-from typing import TypeVar, Union
+from typing import TypeVar, Union, cast
 
 from core.agent.entities import AgentInvokeMessage
 from core.tools.entities.tool_entities import ToolInvokeMessage
@@ -85,7 +85,7 @@ def merge_blob_chunks(
                     message=ToolInvokeMessage.BlobMessage(blob=files[chunk_id].data[: files[chunk_id].bytes_written]),
                     meta=resp.meta,
                 )
-                yield merged_message
+                yield cast(MessageType, merged_message)
                 # Clean up the buffer
                 del files[chunk_id]
         else: