* fix(computer): leave Linux and Windows windows in the background for accessibility actions
Element clicks no longer restore and activate the target window when an
AT-SPI action or UIA Invoke/SelectionItem/Toggle pattern handles them; only
the pointer fallback activates. On Linux, type-text and paste-text insert
into the focused editable field through AT-SPI EditableText without needing
window focus, and fall back to key synthesis or the clipboard otherwise.
Refs #12412
* fix(computer): refuse pointer input after failed activation
* fix(computer): stop after unconfirmed text writes
* fix(computer): insert the full UTF-8 text on Linux
* test(computer): focus each Linux text-entry trial
* fix(computer): verify Linux text mutations before deletion
AT-SPI can acknowledge writes without changing text. Read back
mutation counts and caret state before reporting success.
* fix(computer): verify complete Linux text replacements
* fix(computer): decline unreadable Linux text selections
