Enhance the document icons grid to better handle single-row layouts by
dynamically suppressing column stretching when the number of documents fits
in a single row. Introduce maxColumnsForIconGrid and related logic to
calculate optimal column counts based on container width and icon size.
Update grid style computation to allow optional suppression of single row
stretch, improving alignment and appearance for small document sets.
Add unit tests for icon grid layout calculation and column logic to ensure
correctness across different icon sizes and container widths.
