Quick connect: type user@host into Ctrl+K to open a terminal on a machine without saving it

The desktop had no way to reach a machine that was not in the keychain; the phone has had a manual
box on its terminal screen all along. The palette's query now reads as an address when it has an @
in it: a "not saved" row offers to dial it, Enter asks for the password in place, and a second Enter
connects. Escape on the password step goes back to the address.

It goes through the phone's own path, now split out as VaultViewModel.ConnectToEndpointAsync, so the
tab, the host-key question and the connection-log entry are the same on both heads and nothing is
written to the keychain. Password only, as on the phone: a key is the reason to save the host.

The typed row takes the highlight unless a saved host dials exactly that address, so typing a new
address cannot land on a saved machine whose address merely starts the same way.

Covered by eleven new QuickConnectTests; manual check 7.10a covers the real dial.

src/DodoSSH.Client.App/App.axaml

@@ -1342,6 +1342,19 @@
     <Style Selector="TextBlock.qcrow-subtext">
       <Setter Property="Foreground" Value="{StaticResource TextFaint}" />
     </Style>
+    <!--
+      The palette's typed-address row, which sits above the list rather than in it and so has no ListBoxItem
+      to take :pointerover and :selected from. The same two states, on the row itself.
+    -->
+    <Style Selector="Border.qcrow.adhoc:pointerover">
+      <Setter Property="Background" Value="{StaticResource Hover}" />
+    </Style>
+    <Style Selector="Border.qcrow.adhoc.selected, Border.qcrow.adhoc.selected:pointerover">
+      <Setter Property="Background" Value="{StaticResource Accent}" />
+    </Style>
+    <Style Selector="Border.qcrow.adhoc.selected TextBlock.qcrow-text, Border.qcrow.adhoc.selected TextBlock.qcrow-subtext">
+      <Setter Property="Foreground" Value="{StaticResource AccentInk}" />
+    </Style>
     <Style Selector="ListBoxItem:selected TextBlock.qcrow-text, ListBoxItem:selected TextBlock.qcrow-subtext">
       <!--
         AccentInk rather than a literal white: it is v5's name for "the colour text sits in on top of the