The Data Explorer left-nav resource tree did not expose selection state to
assistive technology. Screen readers announced tree items (e.g. "Documents,
1 of 2, level 3") without conveying whether the item was selected, failing
MAS 4.1.2 (Name, Role, Value).
Selection in the tree is a custom app-state concept (node.isSelected /
shouldShowAsSelected) and does not use Fluent v9's built-in selectionMode.
Wire the existing selection state to the aria-selected prop on TreeItem so
selectable nodes announce "selected"/"not selected". Pure grouping nodes
(no isSelected) omit the attribute, matching the ARIA single-select tree
pattern.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 956998dd-4849-4f7d-a027-b7190018e089
Jade Welton
05d95cb467