Command Palette: Fix macOs label for sites unable to determine UA via PHP

[peterwilsoncc]

What?

Adds a JavaScript check of the User-Agent for displaying the text in the admin bar.

Closes #77636.
See Core-65121

Why?

On sites served over a CDN is it relatively common for the CDN to strip the User-Agent HTTP header, on macOS systems this causes the incorrect label to be displayed.

How?

Adds a JavaScript fallback to test the UA and determine the best label to use.

Testing Instructions

1. Buy a macOS computer/use BrowserStack on macOS.
2. In your wp-config.php file, add the code $_SERVER['HTTP_USER_AGENT'] = ''; to emulate a site behind a CDN stripping the header
3. Visit /wp-admin
4. Ensure the label is correct on this branch.
5. Ensure the label is incorrect on trunk
6. Remove the code added to the wp-config file to avoid confusion later.

Testing Instructions for Keyboard

N/A

Screenshots or screencast

Before	After

Use of AI Tools

N/A

[github-actions]

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Co-authored-by: peterwilsoncc <peterwilsoncc@git.wordpress.org>
Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>

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[github-actions]

Flaky tests detected in 33e7592.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/24975080814
📝 Reported issues:

• [Flaky Test] post title and content are editable and blocks can be inserted #76524 in /test/e2e/specs/editor/various/post-content-focus-mode.spec.js
• [Flaky Test] should disable Save draft button during a multi-file gallery upload #77534 in /test/e2e/specs/editor/various/upload-save-lock.spec.js

[ramonjd]

Just left some questions. 👋🏻

[ramonjd]

do we only care about $_SERVER['HTTP_USER_AGENT']? if so could we skip the fallback if the string exists?

    // If PHP already has a reliable UA, trust it and skip the JS fallback.
    if ( ! empty( $_SERVER['HTTP_USER_AGENT'] ) ) {
        return;
    }

I was wondering why something like

$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/147.0.0.0 Safari/537.36';

wasn't forcing the Ctrl+K. Is it because the JS always loads here?

[peterwilsoncc]

@ramonjd I've switched to navigator.platform as it's more reliable than UA sniffing. Due to the additional reliability I think having the script in place all the time will be helpful. I've also made a few other changes based on the reviews in WordPress/wordpress-develop#11636