Android TV returns to the platform keyboard for single-line fields; the
Flutter overlay stays for multiline and explicit call sites. The bugs
that forced the overlay (#1051, #1079) were an engine show/bind ordering
race, now repaired at the app level:
- MainActivity retries a soft-input show the engine dropped while the
FlutterView was not yet served (flutter/flutter#177360), rebinds the
IME key session once at first show, and consumes leaked D-pad keys
while the keyboard is visible (bounded restartInput budget) so focus
cannot wander behind a stuck keyboard.
- The platform text-input hint is activation-based, so gamepad pause and
the pre-IME D-pad intercept track a live session instead of mere field
focus.
- While a session is live with the keyboard away, Back closes it and is
consumed once, Select re-raises the keyboard, and arrows keep
caret-aware edge-escape navigation instead of dead-ending.
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