Add media embed alignment feature

[jacek-cke]

🚀 Summary

Adds the MediaEmbedStyle plugin to align media embeds, with optional text wrapping.

Configuration options similar to those available in the image style plugins will be delivered in a follow-up ticket: #20131

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📌 Related issues

• Closes Introduce media styles for media embed #2781

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🧾 Checklists

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This does not apply to feature-branch merges.
If an item is not relevant to this type of change, simply leave it unchecked.

Author checklist

• Is the changelog entry intentionally omitted?
• Is the change backward-compatible?
• Have you considered the impact on different editor setups and core interactions? (e.g., classic/inline/multi-root/many editors, typing, selection, paste, tables, lists, images, collaboration, pagination)
• Has the change been manually verified in the relevant setups?
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• Is performance impacted?
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• Have tests been added that fail without this change (against regression)?
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• Are there any changes the team should be informed about (e.g. architectural, difficult to revert in future versions or having impact on other features)?
• Were these changes documented (in Logbook)?

Reviewer checklist

• PR description explains the changes and the chosen approach (especially when performance, API, or UX is affected).
• The changelog entry is clear, user‑ or integrator-facing, and it describes any breaking changes.
• All new external dependencies have been approved and mentioned in LICENSE.md (if any).
• All human-readable, translateable strings in this PR been introduced using t() (if any).
• I manually verified the change (e.g., in manual tests or documentation).
• The target branch is correct.

[pszczesniak]

The two /* istanbul ignore if: paranoid check ... */ annotations don't match ckeditor5-image/src/imagestyle/converters.ts and similar checks in other features:

• Downcast - image-style skips the guard entirely and uses a non-null assertion on mapper.toViewElement(...). I suggest the same here.
• Upcast - image-style has the same !data.modelRange check without coverage suppression. The branch is reachable, so a small test could cover it for real.

Other than that - good job 👍 it looks really good and works as expected :)

[pszczesniak]

You need to add those missing translation keys to the contexst.json in lang folder.

[jacek-cke]

Thanks! All suggestions applied.

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