Grid Multi-Body: Native Vertical Scrollbar & Alignment Spacer

Problem

In the Grid Multi-Body architecture, the bodyWrapper natively handles vertical scrolling (overflow-y: scroll). However, this introduced a 15px layout shift where the grid bodies become horizontally misaligned with the headerWrapper, which lacks a vertical scrollbar.

Solution

1. Remove scrollbar-width: none from bodyWrapper to allow the native vertical scrollbar to be visible at the far right edge of the grid.
2. Dynamically measure the browser's native scrollbar width.
3. Inject a CSS spacer (e.g. padding-right) into the headerWrapper whenever the vertical scrollbar is active to restore perfect horizontal alignment between the headers and the cells.

This resolves the missing vertical scrollbar thumb while preserving zero-jitter native vertical compositing.

Task List

• Modify .neo-grid-body-wrapper CSS.
• Calculate native scrollbar width in JS.
• Update Header.mjs or Container.mjs to inject the compensation spacer.