Add requests observability view

[sorenbs]

Summary

• Add a Requests item under Console in the Studio sidebar and command palette.
• Add a newest-first dummy request explorer with timestamp, service, path, message, and duration columns.
• Add in-place request expansion with Trace and Logs views, including OTel-style spans, external requests, Prisma spans, plain log lines, and structured JSON logs.
• Document the feature, route ownership, and the custom trace timeline UI; add a changeset for @prisma/studio-core.

Validation

• pnpm typecheck
• pnpm exec eslint --fix ui/studio/CommandPalette.tsx ui/studio/CommandPalette.test.tsx ui/studio/Navigation.tsx ui/studio/Navigation.test.tsx ui/studio/Studio.tsx ui/studio/Studio.test.tsx ui/studio/views/requests/RequestsView.tsx ui/studio/views/requests/RequestsView.test.tsx
• pnpm test -- --run ui/studio/Studio.test.tsx ui/studio/Navigation.test.tsx ui/studio/CommandPalette.test.tsx ui/studio/views/requests/RequestsView.test.tsx
• Playwright validation against http://localhost:4310/#view=requests for sidebar navigation, row expansion, Trace, Logs, and structured JSON rendering.

Notes

• Full pnpm test -- --run still reports two unrelated baseline failures in untouched tests: ui/studio/tanstack-db-performance-architecture.test.ts and demo/ppg-dev/build-compute.test.ts.

[github-actions]

Compute preview deployed.

Branch: codex/requests-observability
Service: codex-requests-observability
Preview: https://cmodu1xyt0d6s10o69p3sohut.cdg.prisma.build
Version: https://cv-e19a5e5ce83e.cdg.prisma.build