[dart] Flutter CI beta jobs fail on specify_nonobvious_local_variable_types for pattern variables #4224

On main, the five beta jobs in .github/workflows/flutter_packages_test.yml (dart_a2ui_core (beta), dart_a2ui_cli (beta), dart_a2ui_agent (beta), dart_a2ui_flutter (beta), and dart_a2ui_flutter_example (beta)) fail flutter analyze --fatal-infos with 76 specify_nonobvious_local_variable_types diagnostics across 12 Dart files.

Dart 3.12 (beta) expanded specify_nonobvious_local_variable_types (enabled in the root analysis_options.yaml) to inspect pattern variable destructuring (:final foo and case final foo). Adding explicit types to those 76 pattern bindings satisfies both specify_nonobvious_local_variable_types and omit_obvious_local_variable_types on both stable and beta channels.

_{🤖 Agent-generated}