feat(#2039): list matrix identities in get_agent_meta

hive-c0re/src/socket_server.rs

@@ -417,9 +417,24 @@ async fn handle_get_agent_meta(
         status_set_at,
         hive_name,
         swarm_name,
+        matrix_accounts: read_agent_matrix_identities(target),
     }
 }
 
+/// Read the target agent's matrix identities from the daemon's
+/// `matrix-accounts.json` snapshot (under the agent's state dir).
+/// Best-effort: an absent / unparseable snapshot (no matrix provisioning,
+/// or the daemon not up yet) yields an empty list. The `MatrixIdentity`
+/// serde shape matches the snapshot entries; the snapshot's `live` field is
+/// ignored (only live accounts are written).
+fn read_agent_matrix_identities(agent: &str) -> Vec<hive_sh4re::MatrixIdentity> {
+    let path = Coordinator::agent_notes_dir(agent).join("matrix-accounts.json");
+    std::fs::read_to_string(&path)
+        .ok()
+        .and_then(|s| serde_json::from_str::<Vec<hive_sh4re::MatrixIdentity>>(&s).ok())
+        .unwrap_or_default()
+}
+
 /// `Status` — count of pending (unread) inbox messages for `agent`.
 fn handle_status(coord: &Arc<Coordinator>, agent: &str) -> hive_sh4re::Response {
     match coord.broker.count_pending(agent) {