Add evidence-grounded final diagnosis and controlled human review

src/viano_bug_analysis/case/assembler.py

@@ -84,6 +84,15 @@ class CaseAssembler:
         prior_refs = []
         for _, checkpoint in reversed(chain):
             details = checkpoint["details"]
+            if details.get("operation") in {"diagnosis-start", "diagnosis-complete", "diagnosis-rejected"}:
+                for field in ("context_ref", "diagnosis_ref", "summary_ref", "failure_ref", "error_ref"):
+                    ref = details.get(field)
+                    if ref is None:
+                        continue
+                    if not isinstance(ref, str) or not ref.startswith("analysis/diagnosis/"):
+                        raise CaseBuildError("PREVIOUS_CASE", "Invalid diagnosis checkpoint")
+                    require_file(reader, ref)
+                    excluded.add(ref)
             if details.get("operation")=="investigation-state":
                 for field in ("state_ref","context_ref","summary_ref"):
                     ref=details.get(field)