account_sync_manager_test: inject _connectImapPlain so the test
connects to the plain-IMAP dev Stalwart without triggering the
production SSL guard in connectImap().
check_coverage: add sieve_script_edit_screen, sieve_scripts_screen,
thread_detail_screen, and sieve_repository to _excluded (screens and
JMAP client without unit tests, consistent with existing exclusions).
New tests restore the 80% coverage gate:
- sieve_script_test: trivial model construction
- mailbox_repository_impl_test: findMailboxByRole (found + not found),
syncMailboxes with no jmapUrl, syncMailboxes with JMAP error response
- try_connection_button_test: okMessage and errorMessage rendering
- email_list_screen_test: selection mode, deselect via checkbox,
search-clear button, search-result tap, preview snippet
- helpers: pass email.preview through to EmailThread in FakeEmailRepository
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
