TW-4845 Harden Air cache runtime and provider support

[qasim-nylas]

Summary

• wire Air cache encryption/runtime reconfiguration and preserve attachment/offline queue metadata during migration
• add offline queue integration, cache invalidation, provider support for nylas, and UI fixes for account display/compose focus
• expand Air regression coverage across cache runtime, provider filtering, and Playwright smoke/modal flows

Validation

• go test -count=1 ./internal/air/...
• cd tests && npm run test:air

Jira

• TW-4845