Function render_prompt_text_for_agent 

pub fn render_prompt_text_for_agent(text: &str) -> String

Rewrites user-entered @ lookups into quoted agent-facing path tokens.

File and directory lookups like @path/to/file are rewritten to "path/to/file". Non-lookup uses of @, including email-like tokens and lone @, are preserved so frontends and persisted transcripts can continue storing the original user input unchanged.