refactor: Optimize editor assets endpoint URL processing

[dcalhoun]

Addresses #45319 (comment).

Proposed changes:

Prefer the str_starts_with utility since it is available in PHP 8 and in a polyfill for WordPress 5.9.0 onward. Jetpack requires minimum of WordPress 6.7.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

N/A

Does this pull request change what data or activity we track or use?

No

Testing instructions:

See #45319.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the refactor/optimize-editor-assets-url-processing branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack refactor/optimize-editor-assets-url-processing

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• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

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Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen as soon as you deploy your changes after merging this PR (PCYsg-Jjm-p2).
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  • Scheduled release: October 7, 2025
  • Code freeze: October 6, 2025

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[jp-launch-control]

Code Coverage Summary

This PR did not change code coverage!

That could be good or bad, depending on the situation. Everything covered before, and still is? Great! Nothing was covered before? Not so great. 🤷

Full summary · PHP report · JS report

[kean]

Nice, thanks for following-up on this!