swarm-queue-client: fix AgentState::Destroyed doc, entry never drops out of the set

swarm-queue-client/src/wanted.rs

@@ -92,9 +92,12 @@ pub enum AgentState {
     /// Exists on the hive and is not running.
     Offline,
     /// Torn down entirely — the hive runs the destroy template once, then
-    /// this agent drops out of the declared set rather than staying as a
-    /// third steady state. Irreversible: there is no state that brings a
-    /// destroyed agent back short of a fresh deploy.
+    /// treats absence as agreement rather than re-running it. The key
+    /// stays in the declared set with this state forever, on purpose: it's
+    /// what lets a redeclare of an already-destroyed agent be rejected as
+    /// a terminal-state transition instead of silently reviving it.
+    /// Irreversible: there is no state that brings a destroyed agent back
+    /// short of a fresh deploy.
     Destroyed,
 }