Header grid template columns inadequate for hamburger menu

[ge0rg]

When a site with a long multi-word title is rendered on mobile, the title only has very little horizontal space, leading to line breaks, despite there being plenty of space:

This is due to the significant margins in header_title on the one hand, and due to the default, non-@media grid-template-columns values on the other.

Unfortunately, I fail to understand the semantics of grid-template-columns and so can't provide an adequate fix.