claudetool/codereview: stabilize related files list
diff --git a/claudetool/codereview/differential.go b/claudetool/codereview/differential.go
index 8688843..25defa4 100644
--- a/claudetool/codereview/differential.go
+++ b/claudetool/codereview/differential.go
@@ -1016,9 +1016,12 @@
 		}
 	}
 
-	// Highest correlation first
+	// Highest correlation first, then sort by path.
 	slices.SortFunc(relatedFiles, func(a, b RelatedFile) int {
-		return -1 * cmp.Compare(a.Correlation, b.Correlation)
+		return cmp.Or(
+			-1*cmp.Compare(a.Correlation, b.Correlation),
+			cmp.Compare(a.Path, b.Path),
+		)
 	})
 
 	// Limit to 1 correlated file per input file.