Refactor validators into built-in registry chains

docs/public-contract.md

@@ -10,6 +10,7 @@ This contract covers:
 - transcript/glossary input forms
 - transcript output schema selection
 - process report schema metadata
+- stable validator key identifiers in report/diagnostics records
 - diagnostics directory behavior
 - stdout/stderr and exit-code behavior
 - secret redaction guarantees
@@ -89,6 +90,8 @@ Current values:
 
 `--report-json` output and diagnostics run-dir `report.json` use the same report schema metadata.
 
+Validator decision/rejection records in reports use stable validator keys in `validator_name`.
+
 ## Diagnostics directory behavior
 
 When diagnostics directory creation succeeds, Audita writes run artifacts including: