- Update help UI to show “Ctrl+↑/↓ → resize chat/thinking split”. - Introduce `ensure_ratio_bounds` and `nudge_ratio` on `LayoutNode` to clamp and adjust split ratios. - Ensure vertical split favors the thinking panel when it becomes focused. - Add `adjust_vertical_split` method in `ChatApp` and handle Ctrl+↑/↓ in normal mode to modify the split and update status messages.