Obsctl::TUI::DashboardLayout

The stats pane takes a fixed column rather than a share of the logs row: log lines want every column they can get, and stream health is the same handful of short rows however wide the terminal is. The wider column is used when the row can spare it, because it is what lets the panel print frame totals and the FPS sparkline instead of bare counts.

stats_pane is requested by the caller rather than derived here so the layout stays a pure function of the area. It is honoured only when the logs row can spare the column.