dashboard: transient_set / transient_cleared mutation events + client derived state

hive-c0re/src/dashboard_events.rs

@@ -105,4 +105,20 @@ pub enum DashboardEvent {
         answered_at: i64,
         cancelled: bool,
     },
+    /// A lifecycle action started for an agent (spawn / start / stop
+    /// / restart / rebuild / destroy). Clients render a spinner next
+    /// to the row; the client computes "seconds in this state"
+    /// locally from `since_unix` so a slow rebuild's elapsed time
+    /// ticks without polling.
+    TransientSet {
+        seq: u64,
+        name: String,
+        /// Lifecycle kind: `"spawning"` / `"starting"` / `"stopping"` /
+        /// `"restarting"` / `"rebuilding"` / `"destroying"`.
+        transient_kind: &'static str,
+        since_unix: i64,
+    },
+    /// The matching lifecycle action resolved (success or failure).
+    /// Clients drop the spinner row.
+    TransientCleared { seq: u64, name: String },
 }