Function select_render_mode 

pub fn select_render_mode(
    info: &TerminalInfo,
    force_stream: bool,
    force_tui: bool,
) -> Result<RenderMode, RenderModeError>

Select the render mode based on terminal info and CLI flags.

Priority:

1. --stream flag → Stream
2. --tui flag → Dashboard (requires TTY with sufficient size)
3. Auto-detect from terminal capabilities