style: cap height of artificially-slow example output (#8486)

[lee-eojin]

Fixes #8486

Summary

Expanded Sandpack previews can become excessively tall when an example renders hundreds of list items.

This change caps the affected lists while preserving the original 250/500 item counts and their rendering behavior.

 .items {
+  max-height: 1200px;
+  overflow-y: auto;
 }

This covers:

• Two useDeferredValue examples rendering 250 items
• Four useTransition examples rendering 500 posts

All items are still rendered and remain accessible by scrolling inside the list.

Scope

This change intentionally scopes the height limit to the affected list examples. Applying a global limit to expanded Sandpack previews would affect unrelated examples and may change the intended “Show more” behavior.

Follow-up question

Would you be open to capping the height of expanded Sandpack previews globally?

Currently, “Show more” removes the maximum height entirely. I kept this PR scoped to the affected examples to avoid changing unrelated Sandpacks.

If a global limit is preferred, I can address that separately in a follow-up.

AFTER

Test plan

• Confirmed that all six affected lists have the height limit
• Confirmed that the original 250/500 item counts remain unchanged
• Ran git diff --check
• Visually verified normal and expanded Sandpack modes
• Ran yarn check-all

[github-actions]

Size changes

Details

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