hive-c0re: replace json! with typed structs in dashboard handlers

hive-c0re/src/dashboard/state_snapshot.rs

@@ -726,6 +726,18 @@ pub(super) async fn jobq_rollup(
     axum::Json(state.coord.job_queue.state_rollup())
 }
 
+/// Response body for `/api/dashboard/history`. No `ToSchema` — its
+/// `events` field wraps [`crate::dashboard_events::DashboardEvent`],
+/// which doesn't derive `ToSchema` either (a large enum with many
+/// variants; see that type's doc comment for why annotating it is
+/// out of scope here). The `responses(...)` doc below spells out the
+/// shape in prose instead of a `body = ...` reference.
+#[derive(Serialize)]
+struct DashboardHistoryBody {
+    seq: u64,
+    events: Vec<crate::dashboard_events::DashboardEvent>,
+}
+
 #[utoipa::path(
     get,
     path = "/api/dashboard/history",
@@ -798,7 +810,7 @@ pub(super) async fn dashboard_history(State(state): State<AppState>) -> Response
                     }
                 })
                 .collect();
-            axum::Json(serde_json::json!({ "seq": seq, "events": events })).into_response()
+            axum::Json(DashboardHistoryBody { seq, events }).into_response()
         }
         Err(e) => error_response(&format!("dashboard/history failed: {e:#}")),
     }