Collections: Add column resize and reorder to the DataView table

[priethor]

What

Closes #100
Adds column resize and reorder to the DataView table.

Why

DataViews has no resize handle or reorder hook, so column widths and order were whatever DataViews chose.

How

• DataViewColumnInteractions portals a drag handle and a resize separator into each <th>. The resize handler writes inline widths on every pointermove and commits the final width to view.layout.styles on pointerup. Reorder goes through dnd-kit.
• The dataViewColumns helper holds the per-type min widths, the withColumnWidth / withColumnOrder writers, and normalizeView, which prunes stale style entries and re-pins the title if it falls out of view.fields.
• The table runs in table-layout: fixed with the library's per-cell min-width overridden, so a resized width is the column's actual width.
• Content wrapping: Plain text gets an ellipsis, chips wrap inside their cell, and the header label truncates without clipping its focus ring.

Upstream opportunities

The adapter exists because DataViews has no public column-interaction surface, so there are many opportunities for upstream fixes, which are documented in the tech debt doc.

Testing Instructions

1. Open a page with a DataView block.
2. Drag a column's right edge. Save, reload, confirm the width survives.
3. Double-click the right edge. The column auto-fits to its widest cell.
4. Drag a header sideways past another column's midpoint. The displaced columns slide aside and the drop indicator follows the pointer. Save, reload, confirm the new order survives.
5. Shrink a multiselect column to its minimum. Chips should wrap inside the cell.
6. Shrink a header until the label truncates. The focus ring should still render in full.
7. npm test -- dataViewColumns
8. npm run test:e2e -- data-view-block

Screen recording

Grabacion.de.pantalla.2026-05-01.a.las.13.09.11.mov