The multi-line python3 -c block had unindented Python code that
terminated the YAML block scalar, causing a preExecutionError on every
CI run. Inline the Python as a one-liner.
Also apply dart format to email_repository_impl.dart and fix
avoid_redundant_argument_values lint in email_repository_impl_test.dart.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>