Dashboard: Add compact variant to EmptyState.Wrapper

[StevenDufresne]

Part of #109805

Proposed Changes

• Add isCompact prop to EmptyState.Wrapper that sizes the wrapper to its content instead of filling the remaining viewport height.
• Use compact EmptyState.Wrapper for the blocked sites empty state.
• Add CompactWrapper Storybook story.

Header	Header

Why are these changes being made?

The existing EmptyState.Wrapper always expands to fill the viewport, which doesn't suit all contexts. For example, the blocked sites page just needs a simple card-sized empty state. The isCompact variant removes the min-height calculation and extra padding so the wrapper shrinks to fit its content.

This is an alternative approach to #109805, which addresses the same blocked sites empty state.

Testing Instructions

• Visit the blocked sites page in the Dashboard with no blocked sites — the empty state should render as a compact card.
• Check Storybook: client/dashboard/EmptyState → CompactWrapper story.
• Verify existing EmptyState.Wrapper usage (e.g., empty sites state) is unaffected.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you tested accessibility for your changes? Ensure the feature remains usable with various user agents (e.g., browsers), interfaces (e.g., keyboard navigation), and assistive technologies (e.g., screen readers) (PCYsg-S3g-p2).
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

🤖 Generated with Claude Code

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-174666

Jetpack Cloud Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-174666&env=jetpack

Automattic for Agencies Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-174666&env=a8c-for-agencies

Dashboard Live (dotcom) (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-174666&env=dashboard

Dashboard Live (CIAB) (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-174666&env=dashboard-ciab

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• agents-manager
• blaze-dashboard
• help-center
• notifications
• odyssey-stats
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug add/empty-state-compact-wrapper on your sandbox.