Function msg_fs_sync_from_pty 

pub fn msg_fs_sync_from_pty(
    nonce: u16,
    flags: u16,
    latency_ms: u16,
    inline_max: u32,
    path: &str,
    src_pty_id: u16,
) -> Vec<u8> 

Build a C2S_FS_SYNC whose base directory the server resolves from a pty’s live cwd: sets FS_SYNC_FROM_PTY and appends [src_pty_id:2] last (docs/ide.md Decision 3). path is joined onto the resolved cwd server-side (empty = the cwd itself).