doc: add non-atomicity comment to emit_status RMW (argus note)

hive-ag3nt/src/events.rs

@@ -762,6 +762,15 @@ impl Bus {
         // statuses that shouldn't touch it (e.g. `needs_login_in_progress`
         // is a transient mid-flow status; only `needs_login_idle` and
         // `online` should change the persistent flag).
+        //
+        // Known non-atomicity: this is a read-modify-write. Two concurrent
+        // `emit_status` calls could clobber each other's `needs_login`
+        // change if they raced between the read and the write. In practice
+        // this is safe: the turn loop is sequential and the login flow
+        // (`needs_login_idle` / `online`) only fires outside of active
+        // turns, so the two callers never overlap. Documented rather than
+        // locked because adding a Mutex here would be overkill for the
+        // actual call pattern.
         let (_, current_needs_login) = read_harness_state();
         let new_needs_login = if status == "needs_login_idle" {
             true