Block Supports: Output flex-direction row when a viewport override switches a vertical flex layout to horizontal.

[jorgefilipecosta]

Backport of WordPress/gutenberg#82364.

Currently, when a vertical (Stack) flex layout is set to horizontal on the tablet or mobile viewports, the block stays vertical. The viewport rule only outputs the justification and the base flex-direction: column keeps applying. This PR fixes the issue by outputting flex-direction: row when a viewport override switches the orientation to horizontal.

Trac ticket: https://core.trac.wordpress.org/ticket/66096

Use of AI Tools

AI assistance: Yes
Used for: fix and tests drafted with AI assistance; reviewed and edited by me.

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[github-actions]

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Props jorgefilipecosta.

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[github-actions]

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[talldan]

Thanks, fixes the issue for me on the frontend.

[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 63602
GitHub commit: c176fdb

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.