Improve getting started experience with MCP servers

[meganrogge]

In agent mode, we now show a select tools picker. However, for those unfamiliar with tools/MCP Servers, it's not clear what that will do. I suggest adding a Learn More action or button to the picker.

Additionally, we can refine the placeholder text to help beginners.

For instance, we could include an example of a command to run in the placeholder text for this quickpick:

[meganrogge]

Also, it would be great if there was a add your own config button here so I could directly paste it