Function render_shell 

pub fn render_shell(
    area: Rect,
    buf: &mut Buffer,
    modal: &mut PivotMeltModal,
    border_color: Color,
    active_color: Color,
    text_primary: Color,
    text_inverse: Color,
)

Render the Pivot and Melt modal: tab bar, tab-specific body, footer. Uses border_color for default borders and active_color for focused elements. text_primary and text_inverse are used for text-input cursor (same as query prompt).