Claro primary tabs collapsed menu hamburger icon has insufficient contrast with forced-colors dark background

Problem/Motivation

In forced-colors emulation on MacOS, the "hamburger" menu icon for the collapsed primary tabs (menu local tasks) does not adjust color. On a dark background, the blue icon has insufficient contrast.

I'd guess that this also applies to other platforms, but that needs confirmation.

Steps to reproduce

1. With Claro as the admin theme, go to /admin/content.
2. Do one of:
   • In Chrome or Edge, enable forced-colors: active and prefers-color-theme: dark emulation.
   • In Edge, choose a dark theme under the Page Colors setting.
   • In Firefox, change color the color settings, to get dark background, light text, and yellow links, with "Override" set to "Always".
     
     
3. Reduce the window size until the primary tabs collapse into a menu with the hamburger icon.

Expected

In forced-colors: active mode, the icon color should be ButtonText.

Proposed resolution

Add a media query to the SVG file for (forced-colors: active), specifying currentColor for the fill. This will allow the icon to inherit color from the parent button element in forced-colors mode. 

@Curtis Wilcox also contributed to this proposed resolution.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet