Gallery: make dynamic mode conversion a single undo level

[ramonjd]

What

Switching the Gallery block into or out of dynamic mode now records a single undo level.

Why

enableDynamicMode and convertToStatic each fired two persistent dispatches (replaceInnerBlocks + setAttributes), creating two undo levels. One undo reverted only half the switch, leaving the gallery in a mixed state (dynamic source set with orphaned inner blocks, or vice versa). Reported in #80613.

How

Wrap each action's two dispatches in registry.batch() and mark the second __unstableMarkNextChangeAsNotPersistent(), so both collapse into one undo level. Matches the existing pattern in tab-list, accordion, and quote.

Testing

1. Add a Gallery with a few images.
2. Convert to dynamic ("Use images attached to the post"), then back ("Convert to images").
3. Press undo once. The whole conversion reverts in a single step, in both directions.

Kapture.2026-07-24.at.15.12.16.mp4

[github-actions]

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

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[github-actions]

Size Change: +27 B (0%)

Total Size: 7.75 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-library/index.min.js	355 kB	+27 B (+0.01%)

_{compressed-size-action}

[andrewserong]

This is testing great for me, thanks for fixing it up! I get a consistent single undo level now while undo/redoing across the conversion to dynamic mode and conversion to static mode for the gallery block.

LGTM 🚀

[github-actions]

I just cherry-picked this PR to the wp/7.1 branch to get it included in the next release: f28c82b

[github-actions]

Flaky tests detected in d7c3a5a.
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/30068960876
📝 Reported issues:

• [Flaky Test] does not dirty related template parts or navigation menus when rendered in the post editor #79294 in /test/e2e/specs/editor/blocks/navigation-passive-rendering.spec.js

[Mamaduka]

Thanks, @ramonjd!