The changes remove the `ConditionGroup` abstraction and flatten condition expressions directly under `ConditionBranchConfig.expressions`. This simplifies the data model and evaluation logic, eliminating redundant grouping layers while preserving all functionality. The migration logic and group-level operators are removed as they are no longer needed.
BREAKING CHANGE: `ConditionBranchConfig.expressions` now expects a flat list of `ConditionDetail` instead of `ConditionGroup`; existing configurations must be updated to use direct condition lists.