Full-Bleed Layout Using CSS Grid
The common term for this kind of thing is “full-bleed”. It's a term borrowed from the publishing world; when something is printed full-bleed, it extends to the very edge of the paper.
This new requirement makes the problem considerably more tricky. It's relatively easy to constrain all children, but CSS doesn't really have a mechanism to selectively constrain some children.
Source: CSS Grid full-bleed layout tutorial, an article by Josh W Comeau.