Fx–themed pages briefly show blue links in nav on hover

[janbrasna]

Description

There are pages that override the base type definitions for #15542, which in turn need overriding with higher specificity for global components to stay consistent (for details see #15569 implementing it).

On such pages, hovering the main menu seems to trigger weird effect of briefly flashing the default blue link color (or, perhaps not "default blue", but rather Fx page theme-specific blue) depending on where the pointer is placed.

Steps to reproduce

Move pointer around the main nav on:
https://www.mozilla.org/fr/firefox/challenge-the-default/
https://www.mozilla.org/en/firefox/family/

Expected result

No flash of default/blue link color.

Actual result

Screen.Recording.2025-01-14.at.0.22.58.mov

Environment

WebKit stable, Chromium dev, Gecko beta