Editor: Merge adjacent revision inline diffs

[shail-mehta]

What?

Part of #77530.

Merges adjacent word-level inline revision diffs into fewer <del> / <ins> elements so consecutive edits are grouped instead of marked one word at a time.

Why?

Editor: The editor inconsistently marks up groups of words vs. individual words. E.g., if you've edited several words in a row, it may group them all, group some of them, or have all of them individually in separate del or ins elements. I couldn't figure out why during my testing. However, when they are separate, they significantly increase verbosity for screen reader users.

How?

Add mergeTextDiffParts() in block-diff.js to merge adjacent removed/added tokens into a single removed part and a single added part.

Testing Instructions

1. Create a post, and iterate it several times to create revisions.
2. Open Visual History and enable Show changes.
3. Inspect the paragraph HTML.

Use of AI Tools

• Yes

[github-actions]

Size Change: +127 B (0%)

Total Size: 7.75 MB

📦 View Changed

Filename	Size	Change
build/scripts/editor/index.min.js	499 kB	+127 B (+0.03%)

_{compressed-size-action}

[github-actions]

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[github-actions]

Flaky tests detected in 478e5ad.
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/30017608651
📝 Reported issues:

• [Flaky Test] should update the HTML only for the latest navigation #78835 in /test/e2e/specs/interactivity/router-navigate.spec.ts