Add dev-only observability dashboard

[bartekplus]

Summary

• add a dev-only observability tab and unified runtime snapshot pipeline across background, content, and options contexts
• keep runtime and module state current, including remote registration semantics for forwarded modules
• redesign the observability dashboard UX so module controls and recent events are filterable, scroll-stable, and practical to inspect

Testing

• bun run lint
• bun run format:check
• bun test tests/optionsWorkspacePanels.test.ts tests/settingsEngine.navigation.test.ts
• bun test tests/Logger.test.ts tests/ObservabilityService.test.ts
• bun run build

Notes

• e2e was not run in this branch