Merge branch 'main' into the Android head

Main grew the screens the host-management plan called for — hosts, pins, snippets, logs,
import, teams — plus the ObjectStore and Import projects behind two of them, and moved
WindowsDeviceKeyStore into the desktop head's Platform folder.

Five of those view models landed in a directory this branch had already moved, so they
join the rest in DodoSSH.Client.Shell: git spotted the rename and put them there, and the
namespaces followed. Shell picks up ObjectStore and Import as a result, which the Android
head then gets transitively and will use neither of at first — scoped storage means there
is no ~/.ssh/config to import, and file transfer is out of its first scope.

Desktop suites green at 155 and 64.

src/DodoSSH.Client.App/Views/NavRail.axaml

@@ -5,7 +5,7 @@
              x:DataType="vm:MainWindowViewModel">
 
   <!--
-    Five destinations down the left edge.
+    Six destinations down the left edge.
 
     One of them — TEAM — reaches a screen that says it is not built. It is in the rail anyway rather than
     dropped, and the reasoning is in ShellScreen: the milestones are public, the screen behind it says
@@ -16,6 +16,12 @@
     Buttons rather than a TabStrip or a ListBox, for the same reason the vault's category rail is: all three
     of those hold the selection themselves, so a click moves the highlight before the shell can decide
     anything. Buttons carry no state and cannot disagree with the screen that is showing.
+
+    Lit from IsXShowing and not from IsXScreen, which are different questions now that the tab strip spans
+    every screen. A terminal opened from here leaves Screen on Hosts — deliberately, so closing the tab comes
+    back — and a rail entry lit while a terminal filled the window would be pointing at a screen that is not
+    showing. So nothing here is lit at all while a terminal is up: the selected tab already carries that
+    mark, in the strip, and two "you are here" marks is one too many.
   -->
 
   <Border Width="54" Background="{StaticResource Chrome}"
@@ -23,26 +29,44 @@
     <DockPanel LastChildFill="False">
 
       <StackPanel DockPanel.Dock="Top" Margin="0,8,0,0">
-        <Button Classes="flat nav" Content="HOSTS" Classes.active="{Binding IsHostsScreen}"
+        <Button Classes="flat nav" Content="HOSTS" Classes.active="{Binding IsHostsShowing}"
                 Command="{Binding ShowScreenCommand}"
                 CommandParameter="{x:Static vm:ShellScreen.Hosts}"
-                ToolTip.Tip="Your hosts, and the terminals open on them" />
-        <Button Classes="flat nav" Content="FILES" Classes.active="{Binding IsTransfersScreen}"
+                ToolTip.Tip="Your hosts, and what is known about the one you have selected" />
+        <Button Classes="flat nav" Content="FILES" Classes.active="{Binding IsTransfersShowing}"
                 Command="{Binding ShowScreenCommand}"
                 CommandParameter="{x:Static vm:ShellScreen.Transfers}"
                 ToolTip.Tip="Move files to and from a host over SFTP" />
-        <Button Classes="flat nav" Content="VAULT" Classes.active="{Binding IsVaultScreen}"
+        <Button Classes="flat nav" Content="KEYS" Classes.active="{Binding IsVaultShowing}"
                 Command="{Binding ShowScreenCommand}"
                 CommandParameter="{x:Static vm:ShellScreen.Vault}"
-                ToolTip.Tip="SSH keys, stored passwords, and the host keys you have approved" />
-        <Button Classes="flat nav" Content="TEAM" Classes.active="{Binding IsTeamScreen}"
+                ToolTip.Tip="Your keychain: SSH keys, stored passwords, and the host keys you have approved" />
+        <!--
+          PINS, not HOST KEYS. The rail is 54 pixels wide at mono FontSize 9, which is five characters —
+          and "pins" is what this codebase calls them everywhere else anyway.
+        -->
+        <Button Classes="flat nav" Content="PINS" Classes.active="{Binding IsKnownHostsShowing}"
+                Command="{Binding ShowScreenCommand}"
+                CommandParameter="{x:Static vm:ShellScreen.KnownHosts}"
+                ToolTip.Tip="Host keys you have approved, and how to withdraw one" />
+        <!-- SNIPS, for the same five-character reason as PINS above. -->
+        <Button Classes="flat nav" Content="SNIPS" Classes.active="{Binding IsSnippetsShowing}"
+                Command="{Binding ShowScreenCommand}"
+                CommandParameter="{x:Static vm:ShellScreen.Snippets}"
+                ToolTip.Tip="Commands you have saved, and how to put one into a terminal" />
+        <!-- LOGS, four characters, so it needs no abbreviating at all. -->
+        <Button Classes="flat nav" Content="LOGS" Classes.active="{Binding IsLogsShowing}"
+                Command="{Binding ShowScreenCommand}"
+                CommandParameter="{x:Static vm:ShellScreen.Logs}"
+                ToolTip.Tip="What has been connected to, and what has been changed in this keychain" />
+        <Button Classes="flat nav" Content="TEAM" Classes.active="{Binding IsTeamShowing}"
                 Command="{Binding ShowScreenCommand}"
                 CommandParameter="{x:Static vm:ShellScreen.Team}"
-                ToolTip.Tip="Shared vaults and the people in them. Not built yet — see the screen for what is missing." />
+                ToolTip.Tip="Shared keychains and the people in them. Not built yet — see the screen for what is missing." />
       </StackPanel>
 
       <Button DockPanel.Dock="Bottom" Classes="flat nav" Content="PREFS"
-              Classes.active="{Binding IsPreferencesScreen}"
+              Classes.active="{Binding IsPreferencesShowing}"
               Command="{Binding ShowScreenCommand}"
               CommandParameter="{x:Static vm:ShellScreen.Preferences}"
               ToolTip.Tip="Preferences, and this machine's device key" />