verify(tree, times(1)).release(); // closed in constructor
    }

    @Test
    @DisplayName("open() throwing CIFSException triggers close and rethrow")
    void constructorOpenThrows() {
        // Arrange
        stubAcquireReturnsSelf();
        List<FileEntry[]> pages = List.of(new FileEntry[][] { new FileEntry[] { entry("x") } });

        // Act + Assert