feat(FN-969): scaffold TUI package with Ink entry point and vitest config

- Create @fusion/tui package structure with ink and react dependencies
- Add basic App component entry point using Ink's Box and Text primitives
- Configure vitest with passWithNoTests and coverage settings
- Fix tsconfig to exclude vitest/globals types from production build

packages/tui/src/index.tsx

@@ -1,3 +1,12 @@
 /** @fusion/tui — Terminal UI components for kb */
 
-export {};
+import { render, Text } from "ink";
+import React from "react";
+
+/** Main application component for dev mode */
+function App() {
+  return <Text>Hello from @fusion/tui!</Text>;
+}
+
+// When run directly via `pnpm dev`, render the app
+render(<App />);