Add isCollapsible to the card layout in DataForm

[elazzabi]

What?

This adds support for the isCollapsible field in the card layout. To keep backward compatibility, if the field isn't defined, it defaults to true.

Why?

Non-collapsible cards can be used to display important details or when only one card is present on a page.

Testing Instructions

1. An example is added to the storybook

Screenshots or screencast

[github-actions]

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[github-actions]

Flaky tests detected in ca04f4b.
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/18871775254
📝 Reported issues:

• [Flaky Test] correctly applies dynamic allowed blocks restrictions #51220 in /test/e2e/specs/editor/plugins/inner-blocks-allowed-blocks.spec.js
• [Flaky Test] preserves content in the Custom HTML block #44672 in /test/e2e/specs/widgets/customizing-widgets.spec.js
• [Flaky Test] should refresh the page when stylesheet loading fails #71722 in /test/e2e/specs/interactivity/router-styles.spec.ts

[oandregal]

It'd be nice to have this as an argument to the story, like withHeader is, to act as an educational tool for readers.

[elazzabi]

I agree, I added it and removed this new card. Here's how it looks:

CleanShot.2025-10-23.at.11.45.09.mp4

[oandregal]

I need to check the logic with a fresher brain, and can review later if nobody else beats me to it. But direction looks good.

[oandregal]

@elazzabi the README (see card documentation) needs to be updated as well.

[oandregal]

I've left two comments (README, and useCardHeader hook) I'd like us to address before merging, but this is good to go.