feat(split-screen): redesign split screen with free-form panes and pane picker

src/ui/plugin-host/testing-host.tsx

@@ -253,6 +253,7 @@ export async function renderPlugin(
           label={type}
           isVisible
           isFocusedPane
+          inSplit={false}
           handleRef={null}
           shell={shell}
           {...props}
@@ -276,6 +277,7 @@ export async function renderPlugin(
           label={tab.label}
           isVisible
           isFocusedPane
+          inSplit={false}
           handleRef={null}
           shell={shell}
         />,