extend source and target calculi with observable tick effects + add invariant checks for relation preservation and target arity/shape

src/audit.mli

@@ -2,9 +2,30 @@ type failure_mode =
   | Preserved
   | Representation_exposure
   | Strictness_shift
+  | Effect_shift
   | Type_error of string
   | Other_failure of string
 
+type invariant_kind =
+  | Relation_preservation
+  | Target_arity
+  | Termination_class
+  | Effect_trace
+
+type invariant_result = {
+  kind : invariant_kind;
+  passed : bool;
+  detail : string;
+}
+
+type pass_boundary = {
+  pass : string;
+  source_outcome : Source.outcome option;
+  target_outcome : Target.outcome option;
+  effects : int;
+  verdict : string;
+}
+
 type obligation_status =
   | Discharged
   | Assumed
@@ -27,11 +48,15 @@ type case_audit = {
   typecheck : (unit, string) result;
   failure_mode : failure_mode;
   obligations : obligation_result list;
+  invariants : invariant_result list;
+  pass_boundaries : pass_boundary list;
 }
 
 val audit_case : Corpus.case -> case_audit
 val failure_mode_to_string : failure_mode -> string
 val obligation_status_to_string : obligation_status -> string
+val invariant_kind_to_string : invariant_kind -> string
+val emit_pass_boundaries : case_audit -> string
+val emit_invariants : case_audit -> string
 val emit_case_audit : case_audit -> string
 val emit_matrix : case_audit list -> string
-