fix(datagrid): keep status bar controls clear of the window resize corner (#1569)

[datlechin]

Fixes #1569.

Problem

The last-page pagination button, and the other trailing status bar controls, sat flush in the bottom-right window corner where macOS reserves a 19x19pt live-resize grip. Hovering showed the diagonal resize cursor and the click resized the window instead of activating the button.

Fix

• Inset the status bar so its controls clear the resize corner: trailing 20pt (the macOS content-margin convention, clears the ~10pt grip reach), plus a leading 8pt for balance.
• Add a divider above the status bar so it reads as separate from the data grid.

Status bar cleanup (same area)

• VoiceOver now has explicit labels for the Columns button, the Filters toggle (with a selected trait), and the loading indicators.
• The custom rows-per-page popover now anchors to the page-size menu instead of the center of the pagination controls.
• The loading spinner uses the same control size as the rest of the bar.
• The column visibility popover header is now localizable.

Refactor

• Moved StatusBarSnapshot to Models/Query (Foundation only). It now carries the pagination-visibility predicates, and the row-info text formatting lives in a view-layer extension.
• Collapsed MainStatusBarView's 21-parameter initializer into three callback/state bundles.
• Made the structure-footer inputs non-optional (they are never nil in production) and removed duplicated helpers and section comments.

Tests

• Added StatusBarSnapshotTests covering the row-info text branches and the pagination-visibility predicates.
• The resize-corner inset is layout-only. A UI test asserting the button is inset from the window corner needs database-fixture infrastructure that TableProUITests does not have yet, so it is not included.

Verify when running

The custom rows-per-page popover opens from a menu item. Confirm it presents; it anchors to a stable zero-size overlay on the page-size button.