close worktree transport and lifecycle contract gaps

internal/store/store_test.go

@@ -92,3 +92,18 @@ func TestLifecycleEventsRequireEvidence(t *testing.T) {
 		})
 	}
 }
+
+func TestExpectedVersionIsCheckedForEveryWriter(t *testing.T) {
+	s, err := Open(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Append(created("create")); err != nil {
+		t.Fatal(err)
+	}
+	p := json.RawMessage(`{"reason":"rotate","expected_version":0}`)
+	err = s.Append(domain.Event{Type: "TaskReleased", TaskID: "task-1", Version: 2, Payload: p})
+	if err != domain.ErrConflict {
+		t.Fatalf("expected CAS conflict, got %v", err)
+	}
+}