refactor(workspace): enforce layered crate boundaries

crates/aether-data/contracts/src/repository/candidates/mod.rs

@@ -0,0 +1,10 @@
+mod types;
+
+pub use types::{
+    build_decision_trace, derive_request_candidate_final_status,
+    request_candidate_lifecycle_would_regress, DecisionTrace, DecisionTraceCandidate,
+    PublicHealthStatusCount, PublicHealthTimelineBucket, RequestCandidateFinalStatus,
+    RequestCandidateReadRepository, RequestCandidateRepository, RequestCandidateStatus,
+    RequestCandidateTrace, RequestCandidateWriteRepository, StoredRequestCandidate,
+    UpsertRequestCandidateRecord,
+};