Start fresh workspaces in standard mode

[hamzamerzic]

Summary

• start fresh and fallback workspaces in Standard mode while preserving every valid saved mode
• keep the visible fallback chat or app and the navigation route aligned on first boot
• make Builder-only end-to-end scenarios enter Builder explicitly instead of inheriting a product default

Testing

• npm test (1,989 frontend tests + 63 hook tests)
• npm run build
• syntax-checked every adjusted Playwright scenario
• full hosted backend and browser suites are running on this revision

[hamzamerzic]

Superseded by the reviewed visual integration in #295, which preserves this change and its authorship. The integration is now moving through the merge queue.