Fix quick navigator database selection

[DhruvShah-Dev]

Summary

• use the provider's live selectedDatabases list for quick navigator multi-database items
• align quick navigator multi-database branching with usesMultiDatabaseLayout
• add regression coverage for stale database data being ignored

Testing

• pnpm.cmd exec vitest run tests/utils/quickNavigator.test.ts --pool=forks --maxWorkers=1
• pnpm.cmd typecheck
• pnpm.cmd lint
• pnpm.cmd build

Fixes #591