Restore pilot visual layout

[hlinor-systems]

What changed

• restored the missing editorial page layout and action-button styles;
• added the visual treatment for the Demo data banner;
• documented the visual regression and browser validation.

Root cause

The pilot hardening change added new page states but dropped the existing .content-wrap and .page-intro CSS block. The sidebar and lower workspace stayed styled, while the primary header fell back to browser defaults.

Validation

• npm test — 14 tests passed
• npm run typecheck — passed
• npm run build — passed
• local browser render at 1280 × 720 — visual hierarchy restored
• browser console errors and warnings — none observed