Align content’s width/gutters with topmost banner

[beepdotgov]

At the moment, the main content well and the prototype’s main navigation both have different widths/gutters across breakpoints:

Ideally, the navigation, content, and (to-be-implemented) footer should match each other, and have the same widths. (And if possible, the main navigation should be used as the reference here: the content’s a little too narrow, I think.)

Can this task be done in one increment?

Yes.

Acceptance Criteria

• The prototype’s navigation and content areas have the same widths/gutters across our breakpoints.