KeyboardPlugin.setupInsetsCallback used to early-return on SDK < R, so
the FFI height stayed at 0 on API 29 devices like the Huawei Mate 20 Pro
— the chat composer never tracked the IME. Run the global-layout
listener on all SDKs, and on pre-R also wire setOnApplyWindowInsetsListener
since EMUI 10's IME-hide dispatches new insets without a follow-up layout
pass. Pre-R IME height comes from systemWindowInsetBottom −
stableInsetBottom (stable insets exclude things that animate in/out).
Inside XKeyboard._onFrame, follow notifyListeners with an explicit
scheduleFrame. _onFrame runs as a persistent frame callback after the
build phase has finished, so setState in listeners marks elements dirty
but ensureVisualUpdate is a no-op in this phase — the steady-state pump
masked the issue while the keyboard was open but on the close-edge
(h transitions to 0) the pump stops and the final rebuild was never
scheduled.