UI: Improve how the addon panel work on mobile

[cdedreuille]

What I did

Closes #24424

On the new mobile layout we used to show the addon panel above the canvas. In cases where you use layout: centred the addon panel would hide quite a large part of the UI. To fix that, I replicated the desktop behaviour and made the addon panel appear below the canvas.

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  • bug: Internal changes that fixes incorrect behavior.
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🦋 Canary release

This pull request has been released as version 0.0.0-pr-25787-sha-ce3d85aa. Try it out in a new sandbox by running npx storybook@0.0.0-pr-25787-sha-ce3d85aa sandbox or in an existing project with npx storybook@0.0.0-pr-25787-sha-ce3d85aa upgrade.

More information

Published version	0.0.0-pr-25787-sha-ce3d85aa
Triggered by	@yannbf
Repository	storybookjs/storybook
Branch	charles-fix-mobile-addon-panel
Commit	ce3d85aa
Datetime	Mon Jan 29 11:38:07 UTC 2024 (1706528287)
Workflow run	7695438461

To request a new release of this pull request, mention the @storybookjs/core team.

core team members can create a new canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=25787

[JReinhold]

A few code suggestions, nothing big.

However it poses a problem with large preview sizes, caused by long preview content or just using a large viewport setting. The addon panel won't shrink/cover the preview at all, so if there's no room for preview+panel in the current viewport, the panel just won't show. I think we need to do something about that, I'm not sure what though. Perhaps give the addon panel a min height, and let the preview shrink (scrollable) in that case?

Try this with the "Large mobile" viewport in a small browser window to see how the panel behaves.

https://635781f3500dd2c49e189caf-dyvcpiiyww.chromatic.com/?path=/story/blocks-examples-stories-for-the-canvas-block--layout-centered&globals=viewport:mobile2