feat: seeded transcription-error injection + Recall@k

tests/eval_tests.rs

@@ -0,0 +1,17 @@
+use alpha_id::eval::{inject_errors, recall_at_k};
+
+#[test]
+fn injection_is_deterministic_for_seed() {
+    let a = inject_errors("Diabetes mellitus Typ 2", 0.3, 42);
+    let b = inject_errors("Diabetes mellitus Typ 2", 0.3, 42);
+    assert_eq!(a, b);
+    assert_ne!(a, "Diabetes mellitus Typ 2"); // some corruption at rate 0.3
+}
+
+#[test]
+fn recall_counts_hit_within_k() {
+    let predicted = vec!["E11.9".to_string(), "I10.90".to_string(), "J45.0".to_string()];
+    assert_eq!(recall_at_k(&predicted, "I10.90", 5), 1.0);
+    assert_eq!(recall_at_k(&predicted, "I10.90", 1), 0.0);
+    assert_eq!(recall_at_k(&predicted, "Z99.9", 5), 0.0);
+}