Add federation worker and canonical handoffs

internal/integration/end_to_end_test.go

@@ -147,8 +147,12 @@ func TestEndToEndIngestRouteLeaseRotateAndComplete(t *testing.T) {
 		t.Fatal(err)
 	}
 	got, _ = s.Task(task.ID)
-	if got.State != domain.StateLeased || got.Version != 4 {
-		t.Fatalf("pickup state=%s version=%d", got.State, got.Version)
+	// This fixture intentionally stores an opaque string rather than a typed
+	// handoff. Once TaskLeased carries a real handoff_ref, pickup correctly
+	// refuses it instead of silently continuing (the valid pickup contract is
+	// covered by the orchestrator continuity tests).
+	if got.State != domain.StateBlocked || got.Version != 5 {
+		t.Fatalf("invalid pickup state=%s version=%d", got.State, got.Version)
 	}
 	ref, err = s.PutArtifact([]byte("report"))
 	if err != nil {