It is panicked when prompt length more than 80 and prompt is chinese

[huaweihulk]

PANIC: panicked at src/parser/subagent.rs:817:35:
rust unicode feature

[huaweihulk]

fix from gpt: format!("{}…", &first_line[..80])=>format!("{}…", first_line.chars().take(80).collect::())