Preserve existing content during streaming response errors and enhance error message display

[Emt-lin]

Is your feature request related to a problem? Please describe. Most of the streaming response results were processed successfully, but an error occurred at the end, causing all information to be cleared with only the error visible.

Describe the solution you'd like Add error message in the end of normal message.

chatgpt style:

copilot example:

[Emt-lin]

@ichts It's not be fixed.