Function write_session_title 

pub fn write_session_title(
    session_dir: &Path,
    title: &str,
    generated: bool,
) -> Result<()>

Write a session title into session_meta.json.

generated = true means the title was produced by LLM at the 10th-user-message threshold and should NOT be regenerated on subsequent exits. generated = false means it’s a tentative title (e.g., produced on early exit) that will be regenerated if the session continues to 10 user messages.