Try adding alignment controls to grid layout

[tellthemachines]

What?

Addresses the first part of #62895 (grid parent controls only)

This got complicated because the grid item resize handles follow the item size, which changes if the grid's alignments are other than their default "stretch" value. In order to ensure they work well, we had to do a bunch of changes to the resizer logic.

I've only half reviewed it and have run into a bug while testing where all the grid children become unselectable.

I might not have time to work on this for 7.1, so I'm just leaving this here for now to pick up later.

Testing Instructions

Add a Grid block with children to the page and try changing its justification/alignment. Test with children that have multi-column or multi-row spans.

Use of AI Tools

Written with codex/gpt 5.5.

[github-actions]

Size Change: +1.6 kB (+0.02%)

Total Size: 7.51 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	384 kB	+1.46 kB (+0.38%)
build/styles/block-editor/style-rtl.css	18.7 kB	+32 B (+0.17%)
build/styles/block-editor/style-rtl.min.css	16.1 kB	+37 B (+0.23%)
build/styles/block-editor/style.css	18.7 kB	+38 B (+0.2%)
build/styles/block-editor/style.min.css	16 kB	+37 B (+0.23%)

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