Backporting stable 15.4

[grzegorz-cp]

Proposed changes:

• backporting Jetpack 15.4 stable elease

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?
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Jetpack product discussion

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

Testing instructions:

• Go to '..'

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

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[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 prerelease branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack prerelease

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[Copilot]

Pull request overview

This PR backports the Jetpack 15.4 stable release by updating version identifiers from beta to stable across the codebase.

Key Changes:

• Updated version from "15.4-beta" to "15.4" in plugin files and configuration
• Consolidated beta changelog entries into a single stable release entry
• Fixed a grammatical error in the forms package changelog

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
projects/plugins/jetpack/readme.txt	Updated stable tag and changelog version header from beta to stable
projects/plugins/jetpack/jetpack.php	Updated plugin version header and JETPACK__VERSION constant from beta to stable
projects/plugins/jetpack/composer.json	Updated autoloader suffix to reflect stable version
projects/plugins/jetpack/CHANGELOG.md	Consolidated multiple beta entries into single stable release entry
projects/packages/forms/CHANGELOG.md	Fixed grammatical error (duplicate "to") in changelog entry

[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/jetpack/modules/photon-cdn.php	32/121 (26.45%)	0.83%	-1 💚

Full summary · PHP report · JS report