refactor: unify blob chunk merging logic for plugin tool and agent (#24575)

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

api/core/plugin/impl/agent.py

@@ -8,6 +8,7 @@ from core.plugin.entities.plugin_daemon import (
 )
 from core.plugin.entities.request import PluginInvokeContext
 from core.plugin.impl.base import BasePluginClient
+from core.plugin.utils.chunk_merger import merge_blob_chunks
 
 
 class PluginAgentClient(BasePluginClient):
@@ -113,4 +114,4 @@ class PluginAgentClient(BasePluginClient):
                 "Content-Type": "application/json",
             },
         )
-        return response
+        return merge_blob_chunks(response)