Shift-click range selection differs between admin settings lists and the files table #3741

Initial Checklist

• I understand this is a bug report and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

Bug Description

Shift-click range selection behaves differently in the admin settings lists and in the files table. Cause: useKeyboardTableMouseActions.ts (admin settings) moves the anchor to the last clicked row and adds the range to the existing selection, while useKeyboardFileMouseActions.ts (files) keeps a fixed anchor until a plain click and replaces the selection with the range. The files table also doesn't update the keyboard selection cursor after a Shift+click, so a following Shift+Arrow may deselect rows inside the range (the same gap as in #3738, not verified yet).

Reproduction Steps

1. Admin settings > Groups: click row 1, Shift+click row 3, Shift+click row 5.
2. Files: click row 1, Shift+click row 3, Shift+click row 5.
3. Files: click row 1, Shift+click row 3, press Shift+ArrowUp, then Shift+ArrowDown.

Expected Outcome

Both lists select rows 1-5 the same way (fixed anchor at row 1), and Shift+Arrow after a Shift+click keeps the range contiguous.

Actual Outcome

Admin settings select rows 1-3 plus 3-5 with the anchor moving to row 3; the files table selects 1-5 from a fixed anchor. Step 3 may leave a gap in the files table.