Fine tune when shell integration activation message is shown

[meganrogge]

This will be particularly important when we enable this by default

One option:

• only show it in the first x terminals created of a particular shell

[Tyriar]

Good topic for UX sync, some other ideas:

• Dismiss by hovering the message
• Status bar entry calling out shell integration

[Tyriar]

The message is still there but is now a link to the docs with an action to flip a setting:

[Tyriar]

To verify make sure the link's hover and its links work, even when the link wraps the line in a really narrow terminal.