Method cleanup

tests/test_controller.cpp:86–95

    }

    void cleanup() {
        // Delete controller first (disconnects from editor signals)
        delete m_ctrl;
        m_ctrl = nullptr;
        m_editor = nullptr;  // owned by splitter
        delete m_splitter;
        m_splitter = nullptr;
        delete m_doc;
        m_doc = nullptr;
    }

    // ── Test: setNodeValue writes bytes to provider ──
    void testSetNodeValueWritesData() {