focusSearch() force-focuses the search input and nothing in HeaderBar ever
released it: the Escape arm only fired while the cortinilla was open, and
even then it dismissed the dropdown and left focus in the field. Since the
central dispatcher refuses every binding while a text input holds focus
(AppShell.qml:133-139), the field was a keyboard dead end whose only way out
was a mouse click.
Escape now always dismisses the dropdown if open, accepts, and hands focus
to the shell root via the same isQbzShellRoot duck-walk the modals use.
Clearing focus alone would not do: a null activeFocusItem passes the gate
but leaves AppShell's Keys handler receiving nothing at all.
Reachable from Ctrl+f since the port; the Vim keymap's `/` puts it one
keystroke from the reflex that expects Escape to work, which is how it
surfaced.
Niklas Herder
56be744637