Set CauseStarter tab title from domain branding

[AdamSpitz]

Summary

CauseStarter uses CauseShell rather than AppShell, so the browser tab stayed at Vite's default ui. Domain chrome now sets document.title from branding, and Vite injects the domain name into index.html so the title is correct before JS loads.

Test plan

• UI unit tests (App.test.tsx) cover title on AppShell and CauseShell paths
• Refresh http://localhost:5174/ and confirm the tab says CauseStarter (restart Vite if the HTML plugin was not picked up)

[AdamSpitz]

Review receipt.

Reviewed DomainChrome document.title, Vite index.html title plugin, App tests, and AppShell move. No bugs. One suggestion (DOMAIN_TITLES vs manifests) addressed with a sync comment; Vite cannot import TSX manifests.

Reviewed-with: grok
Reviewed-files: 4
Reviewed-commit: c07a4f1