CDISC validation rule engine: rule-package loader, check evaluator, report assembler and the pluggable report-writer SPI. Ships NO report writer of its own - json/json-2 and xlsx live in cumba-oss-corej-report-json and cumba-oss-corej-report-xlsx - so the engine carries no Excel dependency. Ships the dataviewer's net.cumba.corej.core.* source verbatim.