Agentic UI: Add site overview About summary

[shaunandrews]

Related issues

• Related to Design Exploration: Rebuild the site overview around summary cards #4462
• Stacked on Agentic UI: Add Open in actions to the site overview #4469

How AI was used in this PR

Codex helped extract this focused slice from the larger proof of concept, add the responsive layout and tests, and run the verification workflow. I reviewed the resulting scope and tested the UI in wide and narrow panels in both light and dark themes.

Proposed Changes

• Give each local site a compact About summary with its cached site thumbnail, full active-theme name, and WordPress/PHP versions on one secondary line.
• Restore Classic's browser affordance by making the thumbnail open the site externally, including an always-visible fallback action when no screenshot has been captured yet.
• Introduce a responsive two-column Overview layout so site information sits beside its actions on wide panels while actions remain first when the preview narrows the panel.
• Keep disk usage out of this PR so its filesystem measurement and breakdown can be reviewed as a separate, independently useful follow-up.

Testing Instructions

1. Open a local site's Overview with the preview hidden and confirm About appears beside Customize, Open in…, and Manage.
2. Open the preview and confirm the action sections remain first, with About below them.
3. Confirm the theme name wraps instead of truncating and the versions read as WP v… • PHP v….
4. Click the thumbnail and confirm the site opens in the external browser. Repeat with a site that has no cached screenshot and confirm the empty frame still offers “Open site.”
5. Repeat in light and dark appearance modes.

Automated verification:

• npx eslint --fix on all modified TypeScript/TSX files (CSS files are not covered by the ESLint configuration)
• npm test -- apps/ui/src/components/site-overview-view/index.test.tsx (25 tests)
• npm run typecheck
• npm run cli:build:ui

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[katinthehatsite]

I think this looks good, I already commented in #4473 regarding slightly low contrast on the black arrow and the black background. We can probably make it the same color as the Open site for consistency

A separate question: if a site has a custom domain, should it show in the about section?