Panel: Recommend CollapsibleCard for use outside the block inspector

[Mayank-Tripathi32]

closes #26867

What?

Adds a documentation note to Panel recommending CollapsibleCard for collapsible sections used outside the block inspector.

Why?

Follow-up to #78752. Rather than extending the Panel family with a headingLevel prop, the discussion concluded that Panel is intended for the block inspector sidebar, and CollapsibleCard should be used elsewhere. This documents that guidance.

How?

• Added a note under the Panel README's Development guidelines pointing to CollapsibleCard.

Testing Instructions

• Confirm the rendered Panel README shows the recommendation note linking to the CollapsibleCard Storybook docs.
• Confirm that it is added in correct location for docs.

Use of AI?

• Yes, Claude

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: Mayank-Tripathi32 <mayanktripathi32@git.wordpress.org>
Co-authored-by: aduth <aduth@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: johnwatkins0 <johnwatkins0@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[aduth]

I notice that we recommend this "globally":

gutenberg/packages/components/src/panel/stories/index.story.tsx

Lines 31 to 34 in 1946796

	componentStatus: {
	status: 'recommended',
	whereUsed: 'global',
	},

If what we're saying here and discussed in #26867 is that this component is primarily intended to be used in the editor, then I would suggest we update 'global' to 'editor' to reflect this.

Could you make this update? And remove tags: [ 'manifest' ] as well. For context why this matters, the manifest tag and whereUsed: 'global' are what indicate which components are part of the design system (as discussed in #77159 (comment)). And it sounds like what we concluded in the previous pull request is that this is an editor component, not a general-purpose design system component. CollapsibleCard is already recommended, so no changes are needed there.

[aduth]

This could might be a good use-case for componentStatus.notes in the Storybook, which is often used for this kind of "you might want to use a different component instead in some situations" type guidance.

[aduth]

I'd suggest moving this up higher, maybe even as a plain paragraph under the introduction "Panels expand and collapse multiple sections of content". I'd also suggest removing the > blockquote, since we're not quoting anything.

[Mayank-Tripathi32]

Sure.

[aduth]

LGTM 👍

[Mamaduka]

Thanks for the follow-up, @Mayank-Tripathi32! I think this doesn't require a changelog entry; changes are visible in Storybook and the docs.