fix(datagrid-web): virtual scroll loses scrollbar after column hide

[rahmanunver]

Pull request type

Bug fix

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Description

What: lockGridBodyHeight() in GridSizeStore locked the virtual scroll body height once and only reset it when the page size changed. When a column is hidden, row heights can decrease (text no longer wraps), so the content height drops below the locked max-height — the scrollbar disappears.

Why: The reset condition was incomplete. The existing lockedAtPageSize guard pattern was correct but not applied to column-count changes. The fix adds a parallel lockedAtColumnCount guard: the locked height is now invalidated whenever the visible column count changes, mirroring the existing page-size reset exactly.

Files changed:

• src/model/stores/GridSize.store.ts — added lockedAtColumnCount guard
• src/model/containers/Datagrid.container.ts — wired visibleColumnsCountAtom into GridSizeStore via DI
• src/components/Pagination.tsx, src/components/WidgetFooter.tsx — pre-existing TS7006 implicit-any fixes (were already failing on main)
• e2e/DataGrid.spec.js — regression test: virtual scroll + column hide
• AGENTS.md — architecture reference for the datagrid-web package

What should be covered while testing?

1. Open a page with a Data Grid configured for virtual scrolling and enough rows to produce a scrollbar
2. Confirm the scrollbar is visible in the grid body
3. Open the column selector and hide any column
4. Confirm the scrollbar is still visible after hiding — this was the bug
5. Show the column again and confirm the scrollbar remains consistent