Backing out of a focused text field on TV fires onBack on KeyDown and arms
BackKeyUpSuppressor so the orphaned KeyUp cannot run a second back. When the
closing IME session swallowed that KeyUp entirely, the armed state persisted
and silently consumed the next back press anywhere in the app.
A matching KeyDown now proves the suppressed press ended without its KeyUp
reaching us: the arming clears and the fresh press acts normally. The select
suppressor keeps consuming KeyDowns because the hotkey recorder arms against
the very KeyDown it re-dispatches; KeyRepeat while armed is still consumed.
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