fix(docsite): seed OverflowList properties-tab preview with items

[durvesh1992]

Summary

Closes #2872.

OverflowList's children prop is required, so the docsite properties-tab preview rendered an empty list ("can't render standalone"). Add playground.defaults.children (a few Button items) so the interactive preview shows a real, meaningful list.

packages/core/src/OverflowList/OverflowList.doc.mjs — added playground.defaults.children.

Testing

• Added a preview-state test: buildInitialState resolves the seeded children into 3 elements and getMissingRequiredProps is empty. component-preview-state.test.ts — 9/9 pass.
• Regenerated the docsite data and confirmed the playground children are present in the generated component registry.

Note: the properties-tab preview renders client-side, so I verified the fix at the data/logic level (same approach as the Icon/Skeleton preview fix in #3175). A quick visual check on the running docsite is welcome — I couldn't launch a browser in my environment.

Changeset

Included (@astryxdesign/core patch, docs).

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Project	Deployment	Actions	Updated (UTC)
astryx	Ready	Preview, Comment	Jun 26, 2026 10:08pm

[cixzhang]

Nice! There's a merge conflict.

[cixzhang]

I authorized the preview so we can take a look. We could maybe provide some width to the overflow list's container, and maybe add a default for the overflowRenderer in the playground as well since it only shows one item by default right now. Thanks for working on this!

[durvesh1992]

Thanks for authorizing the preview! Two things, one with a constraint:

1. Width / only one item showing — the list is behavior: 'observeSelf' by default, and in the centered preview it measures ~its own content width and collapses. I can switch the playground default to behavior: 'observeParent' so it sizes to the preview container and shows the full row. (Quick one-line change.)

2. Default overflowRenderer — here's the snag: playground.defaults values are serialized into the generated registry (they go through resolveValue/ElementDescriptors), so they can only be JSON-serializable. overflowRenderer is a (items) => ReactNode function, which can't be expressed there. So the auto-generated Properties preview can't really demonstrate the overflow "+N" affordance.

Given that, I think the cleaner way to show overflow properly (constrained width + a real overflowRenderer "+N" badge) is a dedicated showcase/example block for OverflowList, which is plain code and can include the function. Want me to:

• (a) just add behavior: 'observeParent' here so the Properties preview at least shows the full list, and/or
• (b) add a proper showcase block demonstrating overflow with an overflowRenderer?

Happy to do either/both. (Heads-up: I can't launch a browser in my environment, so I'd lean on your authorized preview to confirm the visual once I push.)