Ensure files cannot be reordered within folders

[sdellis]

Refs #6946

[sdellis]

This screen recording demonstrates the new features that allow for reordering folders, but not files. Files placed in folders are "frozen" at the bottom of each item list. New and pasted folders are now placed at the top (instead of the bottom) of the item list. Any structures that were saved with intermingled files will load with all files frozen at the bottom, ensuring backwards compatibility.

Screen.Recording.2026-01-22.at.10.38.37.AM.mov