Make the host pane something you ask for, and draw it as cards

THE DRAWER USED TO ARRIVE WITH THE SELECTION. IsDrawerOpen read "a host is
selected", so touching any card took 304 pixels off the grid — including every
card arrowed past on the way to the one somebody wanted. Choosing among forty
machines was charged the price of the pane for one of them. A pencil now appears
on the card under the pointer and on the selected card, and that is what opens
it; IsHostPaneOpen is the flag, and the grid's context menu gained Details… so
the pane is reachable without a pointer, which a hover-only control is not.

Once open it follows the selection rather than pinning the host it was opened
on: a pane about one host beside a grid marking a different one is two answers
to the same question. Losing the selection closes it and clears the flag, or a
filter matching nothing would leave the pane armed to spring open again on the
next card merely selected — which is the behaviour the pencil exists to remove.

The pencil is drawn over the card rather than in a column of its own. A column
would have cost the name 30 pixels of a 232-pixel tile, permanently, for a
control that is only there while the pointer is; the dot and the pencil stack in
the two corners of that edge instead. IsVisible and not opacity, because a
button at zero opacity still takes the click and the card underneath does not.

A HEADER, A BODY THAT SCROLLS, AND A FOOTER, which is the one structural change
in the pane. The header names what the drawer is about and carries the two
things true of every panel; the footer carries the one thing each panel is for —
CONNECT, or SAVE, or the question about deleting. Only the middle scrolls, so
the button somebody came here to press can no longer be below the fold, which
CONNECT could be on a host with fifteen tags. That also widens what the layout
harness certifies: it skips anything inside a ScrollViewer, and the control each
panel exists to offer is now outside one.

THE SAME THREE CARDS TWICE. Address, General, Connection — first as rows stating
what the host is, then as boxes for changing it. The detail pane's rows are
buttons that open the editor: the design draws every fact as a filled box, and
rather than draw an input that refuses the pointer, pressing one leads to the
same card with a real box in it. Nothing here saves as you type, and that is not
timidity — saving validates the key-or-credential exclusion and writes one
encrypted payload, so a box committing per keystroke would be a save per
character and a half-typed hostname on the wire.

Every value the pane prints is the resolved one, and says "inherited" beside it
where a group supplied it. The number is the same either way and the edit is
not: clearing a group's default moves every host that never overrode it.

A HOST CARD IS TWO LINES AND NO CHIPS. The subtitle is now "ssh, root, pci,
eu-west-1" — the transport, the resolved account, then every tag — replacing
both the user@host:port line and the wrapped row of tag chips under it. The
address went to the card's tooltip rather than nowhere: a card is read while
scanning forty machines, where the name and the kind of machine are what is
being looked for, and an address is what you read once you have found it.

"ssh" is a constant today and is printed anyway, which is the one thing here
that argues with this codebase's own rule about constants dressed as readings.
It is the first item of a list whose other items vary, and a list beginning with
the account on one card and a tag on the next has no shape to scan. The remark
on HostRowViewModel.Summary says so rather than leaving it to be discovered.

WHAT THE DESIGN DRAWS AND THIS PANE HAS NOT GOT: Share this host, Add Telnet,
"SSH ID, Certificate, FIDO2", the backspace-key mapping row, the vault picker's
chevron and Show more. Sharing is per vault and not per item, every session here
is an SSH channel, there are no identity or certificate item types, nothing
carries a terminal setting to the renderer, and an item cannot be moved between
vaults at all. Six controls with nothing behind them, listed in
docs/design-import-gaps.md with what ships instead, and none drawn disabled.

The credentials row is marked with ◆ rather than the ⚿ the nav rail uses for the
keychain. U+26BF is outside both faces this application substitutes for the
design's fonts, so it lands on whatever the platform's fallback has; every other
glyph in the pane is from Geometric Shapes, which both carry.

tests/DodoSSH.Client.App.Layout.Tests/ScreenLayoutTests.cs

@@ -143,10 +143,17 @@ public sealed class ScreenLayoutTests : IAsyncLifetime
     // and lost the list; see HostDrawer. What it is measured at changed with it: 304 rather than 268, and on
     // the right.
 
+    /// <remarks>
+    /// Opened through the command rather than by assigning the selection, which is the whole of what changed
+    /// when the pencil arrived: a selected host no longer puts the pane up, so a test that only selected one
+    /// would measure a drawer with all three panels collapsed and pass on an empty column. See
+    /// <c>VaultViewModel.IsHostPaneOpen</c>.
+    /// </remarks>
     [Fact]
     public async Task TheHostDrawerFitsShowingAHost()
     {
-        vault.SelectedHost = vault.Hosts[0];
+        vault.OpenHostPaneCommand.Execute(vault.Hosts[0]);
+        vault.IsShowingHostDetail.ShouldBeTrue("there is nothing to measure otherwise");
 
         await MeasureDrawerAsync(faults => faults.ShouldBeEmpty());
     }
@@ -206,8 +213,8 @@ public sealed class ScreenLayoutTests : IAsyncLifetime
     [Fact]
     public async Task TheHostDrawerFitsWithADeletionInQuestion()
     {
-        vault.SelectedHost = vault.Hosts[0];
-        vault.SelectedHost.IsConnected = true;
+        vault.OpenHostPaneCommand.Execute(vault.Hosts[0]);
+        vault.SelectedHost.ShouldNotBeNull().IsConnected = true;
 
         vault.DeleteHostCommand.Execute(null);
         vault.IsConfirmingDeletion.ShouldBeTrue();
@@ -373,7 +380,7 @@ public sealed class ScreenLayoutTests : IAsyncLifetime
     [Fact]
     public async Task TheHostsScreenFitsWithTheDrawerOpen()
     {
-        vault.SelectedHost = vault.Hosts[0];
+        vault.OpenHostPaneCommand.Execute(vault.Hosts[0]);
         vault.IsDrawerOpen.ShouldBeTrue();
 
         await MeasureHostsAsync(faults => faults.ShouldBeEmpty("with a host selected and the drawer out"));
@@ -399,7 +406,7 @@ public sealed class ScreenLayoutTests : IAsyncLifetime
     [Fact]
     public async Task TheHostsGridKeepsTwoColumnsAtTheMinimumWithTheDrawerOpen()
     {
-        vault.SelectedHost = vault.Hosts[0];
+        vault.OpenHostPaneCommand.Execute(vault.Hosts[0]);
         vault.IsDrawerOpen.ShouldBeTrue("the drawer is what takes the width away");
 
         await OnTheHostsScreenAsync((screen, window) =>