swarm: add a declared "paused" agent wanted state

mara (#4170): swarm-ui's wanted-state dropdown could only ever declare
up/offline/destroy, with no way to swarm-declare the existing hive-local
turn-loop pause (`hivectl agent pause|resume`).

`AgentState::Paused` is not a fifth peer of Up/Offline/Destroyed on the
power axis this enum otherwise answers — it's Up plus an orthogonal
turn-loop pause. `hive-c0re`'s `workers::wanted` reconcile loop now
decides the two axes independently (`decide` for power, the new
`decide_pause` for the marker), so a stopped agent declared Paused
converges with both a Start and a Pause in the same pass.

Known, deliberate limitation: a Paused declaration on an agent this
hive has never deployed only reaches Deploy this pass — writing the
pause marker into a harness dir that may not exist yet was judged not
worth the risk, so it converges on the next pass once the agent is
present instead.

swarm-ui's WantedMenu gains a fourth "paused" option (warning-tone
badge). No separate "resume" entry — selecting "up" from a paused row
already clears the marker via the same decide_pause path.

Pause/resume marker writes go through one shared
Coordinator::set_paused_by_name helper, used by both the interactive
dashboard pause/resume handlers and this reconcile loop, instead of
each duplicating the parse-name/write-marker/track-rescan shape.
swarm-ui's "offline" and "paused" confirm dialogs share one
confirmTarget state and one ConfirmDialog instead of two near-identical
copies.

Closes #4170

swarm-queue-client/src/wanted.rs

@@ -91,6 +91,14 @@ pub enum AgentState {
     Up,
     /// Exists on the hive and is not running.
     Offline,
+    /// Exists on the hive, is running, and its turn loop is parked — the
+    /// swarm-declared counterpart of the hive-local `hivectl agent pause`
+    /// marker. Orthogonal to the power axis `Up`/`Offline` express: a
+    /// paused agent still has a running container (the web UI and MCP
+    /// daemons stay reachable), it just drives no turns. See
+    /// `hive-c0re::workers::wanted::decide_pause` for the convergence side
+    /// of that split.
+    Paused,
     /// Torn down entirely — the hive runs the destroy template once, then
     /// treats absence as agreement rather than re-running it. The key
     /// stays in the declared set with this state forever, on purpose: it's
@@ -111,6 +119,7 @@ impl AgentState {
         match self {
             AgentState::Up => "up",
             AgentState::Offline => "offline",
+            AgentState::Paused => "paused",
             AgentState::Destroyed => "destroyed",
         }
     }
@@ -220,12 +229,12 @@ mod tests {
 
     #[test]
     fn the_known_states_decode_and_round_trip() {
-        let doc =
-            r#"{"agents":{"a":{"state":"up"},"b":{"state":"offline"},"c":{"state":"destroyed"}}}"#;
+        let doc = r#"{"agents":{"a":{"state":"up"},"b":{"state":"offline"},"c":{"state":"destroyed"},"d":{"state":"paused"}}}"#;
         let decoded: HiveWanted = serde_json::from_str(doc).expect("decodes");
         assert_eq!(decoded.agents["a"].state, AgentState::Up);
         assert_eq!(decoded.agents["b"].state, AgentState::Offline);
         assert_eq!(decoded.agents["c"].state, AgentState::Destroyed);
+        assert_eq!(decoded.agents["d"].state, AgentState::Paused);
         assert_eq!(serde_json::to_string(&decoded).expect("serialises"), doc);
     }
 
@@ -237,7 +246,10 @@ mod tests {
     /// the round-trip test above proving the happy path still works.
     #[test]
     fn an_unknown_state_fails_the_whole_declaration() {
-        let doc = r#"{"agents":{"a":{"state":"up"},"c":{"state":"paused"}}}"#;
+        // `"paused"` used to be this test's unknown example; it is a real
+        // variant now, so `"sleeping"` takes its place as one this build
+        // still does not know.
+        let doc = r#"{"agents":{"a":{"state":"up"},"c":{"state":"sleeping"}}}"#;
         assert!(serde_json::from_str::<HiveWanted>(doc).is_err());
     }
 
@@ -264,10 +276,18 @@ mod tests {
     /// to compile here rather than quietly going untested.
     #[test]
     fn as_str_matches_the_serde_spelling() {
-        let every = [AgentState::Up, AgentState::Offline, AgentState::Destroyed];
+        let every = [
+            AgentState::Up,
+            AgentState::Offline,
+            AgentState::Paused,
+            AgentState::Destroyed,
+        ];
         for state in every {
             match state {
-                AgentState::Up | AgentState::Offline | AgentState::Destroyed => {}
+                AgentState::Up
+                | AgentState::Offline
+                | AgentState::Paused
+                | AgentState::Destroyed => {}
             }
             assert_eq!(
                 serde_json::to_string(&state).expect("serialises"),