fix: route calls only through ready IMS sessions

internal/server/call_api.go

@@ -203,7 +203,11 @@ func (s *Server) hangupVoWiFiAfter(deviceID, callID string, duration time.Durati
 
 func (s *Server) callTransport(deviceID string) string {
 	if s.vowifi != nil {
-		if state, err := s.vowifi.State(deviceID); err == nil && state.Enabled {
+		// Enabled is only the desired card policy. Calls can use IMS only after
+		// registration has actually completed; otherwise keep using the modem's
+		// circuit-switched call path instead of routing into an unavailable IMS
+		// session.
+		if state, err := s.vowifi.State(deviceID); err == nil && state.IMSReady {
 			return "vowifi"
 		}
 	}

internal/server/call_api_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"vocat/internal/modem"
+	"vocat/internal/vowifi"
 )
 
 func TestParseCLCC(t *testing.T) {
@@ -28,3 +29,15 @@ func TestValidDialNumber(t *testing.T) {
 		}
 	}
 }
+
+func TestCallTransportRequiresIMSReady(t *testing.T) {
+	controller := &fakeVoWiFiController{state: vowifi.State{Enabled: true}}
+	server := &Server{vowifi: controller}
+	if got := server.callTransport("ec20"); got != "cellular" {
+		t.Fatalf("callTransport before IMS registration = %q, want cellular", got)
+	}
+	controller.state.IMSReady = true
+	if got := server.callTransport("ec20"); got != "vowifi" {
+		t.Fatalf("callTransport with IMS ready = %q, want vowifi", got)
+	}
+}