Core state machine, deterministic hashing, mutation catalog and report writers. Pure Java 17. ARCHITECTURAL INVARIANT: this module must contain ZERO Spark imports. It has no compile- or provided-scope dependency on any org.apache.spark artifact, and scripts/check_no_spark_imports.sh fails the build if an "import org.apache.spark" statement appears in src/main/java. SessionResetFacade is the deliberate edge case: its logic is entirely Spark-specific but it is ...