Hand Android's own focus back to the terminal after an accessory key

Focusable=false was only ever half the fix, and its remark now says so:
Avalonia's focus stays on the NativeWebView, but the touch that presses
a key still hands Android's native focus to Avalonia's input view — the
platform moves it before Avalonia decides anything. The WebView's input
connection dies with it, the keyboard swaps to its no-input layout, and
the inset churn parks it over the very row that was tapped.

Each key now returns that focus once its byte is on the wire, through a
sibling of SoftKeyboard that walks the decor view to the one WebView
this application has. Free when nothing moved. Check 11.10a is the
phone-in-hand proof.

docs/manual-checks.md

@@ -1745,6 +1745,21 @@ is a terminal that answers the buttons and ignores the keyboard: it reads as the
 Worth doing on the software keyboard too, where the same fault shows as the keyboard closing on the first
 tap of an arrow key.
 
+### 11.10a The accessory keys do not cost the terminal its *software* keyboard either
+
+With a shell open and the software keyboard up, tap **esc**, **tab** or an arrow on the accessory row, then
+keep typing on the software keyboard.
+
+**Pass:** the keyboard does not change — not its layout, not its suggestion strip, not its height — and
+everything typed after the tap still reaches the terminal. The accessory row stays visible above the
+keyboard throughout.
+
+**Failure means:** Android's own view focus stayed on Avalonia's input view after the tap instead of being
+handed back. This is the half `Focusable = false` cannot reach — the platform moves its focus on the touch
+itself, before Avalonia decides anything — and the symptom chain is the keyboard swapping to its no-input
+layout and the inset churn parking it over the very row that was tapped. See
+`TerminalFocus` in the Android head's Platform folder.
+
 ### 11.11 Closing a connection and opening a new one both take you somewhere real
 
 Open a shell, close its tab, then open a different one from HOSTS.