No :focus state on the home icon (`.wp-admin-bar-site-name a`) in mobile viewports

[joedolson]

Exists at least into 7.0, but I haven't yet explored further back.

In the attached screenshot, both the menu link and the home link have assigned :focus in the browser tools, but only the menu link changes visual state.

[joedolson]

Mobile admin focus states on home and menu

Trac ticket: https://core.trac.wordpress.org/ticket/65765

The home icon is drawn on .ab-item::before and has no nested .ab-icon span. In mobile layouts its resting colour is more specific than its focus colour, so focusing the link never changes the icon:

resting #wpadminbar.mobile .quicklinks .ab-item:before (1,3,1)
focus #wpadminbar li .ab-item:focus:before (1,2,2)

This adds a focus selector next to the existing .hover rule, at matching specificity (1,4,1).

Both files are needed. colors/_admin.scss generates the admin colour schemes. admin-bar.css handles the two cases that load no colour scheme file at all: the Fresh scheme, and the toolbar on the front end of the site.

[!NOTE]
#wpadminbar only gets the mobile class when wp_is_mobile() returns true, so reproducing needs a device preset in DevTools or a real device — narrowing the browser window is not enough.

## Screenshots

	Before	After
Admin
Front end

The front-end pair also shows the mechanism: site-name and site-editor draw their icons on .ab-item::before and gain a focus colour with the patch, while comments uses a nested .ab-icon and was already working.

## Use of AI Tools

• AI assistance: Yes
• Tool(s): Claude Code
• Model(s): Claude Opus 5
• Used for: Investigating the CSS specificity conflict, verifying the behaviour across the admin colour schemes and the front-end toolbar, and drafting the commit message and this description. The final change was reduced, tested and confirmed by me.

[afercia]

This will be fixed in #65445.

[afercia]

In 63009:

Toolbar: Improve the focus style indication.

• Updates the toolbar items styling by adding a more prominent focus indicator.
• Adjusts label and icon coloring selectors (including mobile-specific focus states).
• Refines the 'Howdy menu' dropdown layout and focus styles.
• Tweaks the responsive menu toggle item sizing.

Props afercia, joedolson, sabernhardt, khokansardar, jns141191, iamraju, sukhendu2002, shamimmoeen, ugyensupport.
Fixes #65445.
Fixes #65765.