Desktop ListBox designer preview ignores ColumnWidths and default header captions

The desktop window designer's ListBox preview ignored the configured ColumnWidths schema and never showed header captions: every column rendered at equal width, and columns without a stored header entry appeared blank even though the running application shows its default "Column 0", "Column 1", … captions. The preview now resolves column widths with the same contract as the runtime and shows the runtime's default captions for unstored headers.