fix(tui): raise ink maxFps to 60 to stop flickering

The flicker was coming from the renderer path, not from chat state
churn.

`Input.tsx` keeps typing local to `@inkjs/ui`’s `TextInput`, so the
whole chat transcript is not re-rendering on every keypress.

The actual hot path is `tui.tsx`, where Ink renders the terminal UI
and throttles frame updates.

TextInput redraws the line on each keystroke, including the inverse-video
cursor; when you type faster than the default render cadence, some
terminals show that as flicker/skipped repaint.

Raising `maxFps` does not change app behavior, just lets the TUI flush
input updates more smoothly.

Author: remarkablemark

src/tui.test.tsx

@@ -36,6 +36,7 @@ describe('tui', () => {
 
     expect(render).toHaveBeenCalledWith(expect.anything(), {
       incrementalRendering: true,
+      maxFps: 60,
     });
     expect(screen.setClearHandler).toHaveBeenCalledWith(expect.any(Function));
 

src/tui.tsx

@@ -7,6 +7,7 @@ export function renderApp(): void {
   const tree = <App />;
   const app = render(tree, {
     incrementalRendering: true,
+    maxFps: 60,
   });
 
   screen.setClearHandler(() => {