[rd-code-23]

Summary

• wire the welcome page guest button to create a tab-scoped guest marker and open /dashboard
• clear guest mode whenever the welcome route is entered
• redirect successful Google sign-ins to /dashboard by default
• add a neutral temporary dashboard landing page shared by guest and authenticated entry
• cover guest-state transitions and the Google default return path

Testing

• pnpm lint
• pnpm typecheck
• pnpm test (61 tests passed)
• pnpm build

Note

pnpm format:check still reports seven pre-existing formatting issues outside this change. All files in this PR were formatted and passed the pre-commit formatter and linter.

Refs #13