Function layout 

pub fn layout(rect: Rect, model: bool, policy: bool) -> Panels

Lays the panels out: the maps and the chart in one row when the canvas is wide enough for full-height maps (or nearly), else the maps above the chart, side by side when two fit at a readable size.

The policy panel, when shown, is a strip POLICY_HEIGHT tall across the canvas’s bottom, and the other panels share the rest as without it.