lifecycle: leak the stop-failed warning kind once per agent

Closes #6096

hive-c0re/src/lifecycle/tests.rs

@@ -422,3 +422,27 @@ fn a_build_without_a_log_row_has_an_empty_build_id() {
     assert_eq!(field(&logged[0].1, "build_id"), Some(""));
     assert_eq!(field(&logged[0].1, "agent"), Some("alice"));
 }
+
+#[test]
+fn stop_kind_is_leaked_once_per_agent() {
+    let first = stop_kind("stopkind-a");
+    assert_eq!(first, "agent_stop_failed_stopkind-a");
+    assert!(std::ptr::eq(first, stop_kind("stopkind-a")));
+    assert!(!std::ptr::eq(first, stop_kind("stopkind-b")));
+}
+
+#[test]
+fn stop_kind_survives_a_clean_stop_between_failures() {
+    let failed = |guards: &mut std::collections::HashMap<_, _>| {
+        let kind = stop_kind("stopkind-c");
+        guards.insert(
+            "stopkind-c".to_owned(),
+            crate::warnings::set_warning(kind, "crit", "stop failed"),
+        );
+        kind
+    };
+    let mut guards = std::collections::HashMap::new();
+    let first = failed(&mut guards);
+    guards.remove("stopkind-c");
+    assert!(std::ptr::eq(first, failed(&mut guards)));
+}