fix(ambient): re-check active mode after the judge call (coexistence TOCTOU)

internal/ambient/sentinel.go

@@ -236,6 +236,16 @@ func (s *Sentinel) evaluate(ctx context.Context) {
 	cancel()
 
 	s.mu.Lock()
+	// A mode may have activated during the (off-lock) brain call; re-check so a
+	// result computed while idle is not surfaced over an now-active mode.
+	if s.activeModeLocked() != "" {
+		changed := s.clearLocked()
+		s.mu.Unlock()
+		if changed {
+			s.fireOnChange()
+		}
+		return
+	}
 	s.lastEvalTitles = joined
 	if err != nil {
 		s.mu.Unlock()