Differentiate App Router error pages by error type
- Server errors (digest present): "This page failed to load" with error reference
- Client errors (no digest): "This page crashed" with Go back button
Changes:
- Create shared error-styles.tsx for DRY styling between error pages
- Update global-error.tsx with server/client differentiation
- Update app-error.tsx (static 500) for server error messaging
- Revert Pages Router _error.tsx to canary (keep original simple design)
- Update all affected test assertions
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
