Backport: Mozilla rebrand button and link styles

[maureenlholland]

We've encountered some specificity issues on bedrock as we overrode existing Protocol styles to apply the rebrand styles. Making these changes upstream should allow us to removed a lot of workaround or rebuilt code:

• https://github.com/mozilla/bedrock/blob/main/media/css/m24/components/navigation-refresh.scss#L360
• https://github.com/mozilla/bedrock/pull/16078/files#diff-a3acc966d642d1704d21597a1427686bfee52ae31c611feaa68ea3932ee78ea9R96

Updating links and buttons together seems useful as they are sometimes styled by class instead of element.

mozilla/bedrock#15873
mozilla/bedrock#15925 (might not be rebrand-related but good chance to fix generally related issue)

[janbrasna]

I believe the above screen shot is nonetheless a bug unrelated to refresh styles, as I have documented the same pre-refresh #842 — hopefully the proposed fix will resolve most of the defaults in one update.

But yes, until the m24 "theme" is defined as MZP theme, overriding overrides will be endless…

[maureenlholland]

possibly a chance to simplify some of the specificity around link element and remove some mixins: #1045 (comment)

[janbrasna]

Not sure if this mozilla/bedrock#15803 (comment) is expected:

Screen.Recording.2025-04-23.at.17.57.47.mov

so I'm adding it here to keep track of a rather nice demonstration of interaction between the themes, and the global components partially adhering to the theme, and partially enforcing M24 styles no matter what.

[stephaniehobson]

There's also a medium sized button in the new system that needs to be added mozilla/bedrock#15563.