Add local::lib's dir to .gitignore
Issues #28636: Articles setup warning appearance

The commit adcb24554 just fixed the issue for the title part of
the titlebox. Thus, we need to fix the issue with the box itself
extending outside of the gray borders.

The issue was introduced in 61e7290e when the theme was created
which seems to be an attempt to style the display of simple error
msgs rendered by Elements/Error which is not in the titltebox
context.

The fix here was to make the pages using a titlebox to display an
error msg to use a different error class than just "error", that is,
now called "error-titlebox".