Fix: Restore clickable terminal link hover

[Rishi1878]

Fixes #273097

This PR restores mouse-only clickable behavior for terminal links in the integrated terminal. Previously, the _getLinkHoverString function escaped the URI and label using appendText(), which stripped markdown formatting and rendered the link as plain text.

🔧 Fix:

• Removed unnecessary escaping of uri and label
• Used appendLink() directly to preserve clickable behavior

✅ Tested:

• Hover displays clickable link
• Modifier key hint appears
• Link opens on mouse click without keyboard
• Verified across reloads and multiple terminal sessions