Add underline styling to Link component

[Copilot]

The Link component rendered clickable text without visual indication of interactivity. This addresses feedback to add underline styling consistent with link styles elsewhere in the codebase (theme.tsx).

Changes:

• Added underline={true} prop to the <text> element in Link component

Before:

<text fg={props.fg} onMouseUp={() => { ... }}>
  {displayText}
</text>

After:

<text fg={props.fg} underline={true} onMouseUp={() => { ... }}>
  {displayText}
</text>

This affects authorization URLs in the provider authentication flow, making them visually distinct as clickable elements.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[Copilot]

Pull request overview

This PR adds underline styling to the Link component to improve visual indication of clickable elements in the terminal UI. The change aligns with existing markdown link styling patterns defined in the theme configuration.

• Added underline={true} prop to the Link component's text element for better visual affordance

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.