tui: remove footer overlay when sidebar is hidden to improve screen real estate

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx

@@ -1028,9 +1028,6 @@ export function Session() {
                 sessionID={route.sessionID}
               />
             </box>
-            <Show when={!sidebarVisible()}>
-              <Footer />
-            </Show>
           </Show>
           <Toast />
         </box>