Desktop: rebuild the hosts board once the typing in the find box pauses, not once a letter

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

@@ -520,6 +520,53 @@ public sealed class HostGridTests : IAsyncLifetime
         });
     }
 
+    /// <remarks>
+    /// Every change to the filter rebuilds the board's sections and every card in them, and a name typed at
+    /// speed used to do that once a letter. The box now tells the vault once the typing pauses — and then
+    /// exactly once, with the whole of what was typed.
+    /// </remarks>
+    [Fact]
+    public async Task TypingIntoTheFindBox_RebuildsTheBoardOnceThePauseComes_NotOnceALetter()
+    {
+        await OnTheBoardAsync((screen, _) =>
+        {
+            // Each letter's wait, ended by hand: the pause is real time in the application, and this says
+            // when it is over instead of sleeping through it.
+            var pauses = new List<TaskCompletionSource>();
+
+            screen.Pause = _ =>
+            {
+                var pause = new TaskCompletionSource();
+                pauses.Add(pause);
+                return pause.Task;
+            };
+
+            var rebuilds = 0;
+            vault.HostSections.CollectionChanged += (_, _) => rebuilds++;
+
+            var box = screen.FindControl<TextBox>("HostFilter").ShouldNotBeNull();
+
+            box.Text = "p";
+            box.Text = "pr";
+            box.Text = "pro";
+            Dispatcher.UIThread.RunJobs();
+
+            vault.HostFilter.ShouldBeNullOrEmpty("nothing has reached the vault while the typing goes on");
+            rebuilds.ShouldBe(0);
+
+            foreach (var pause in pauses)
+            {
+                pause.SetResult();
+            }
+
+            Dispatcher.UIThread.RunJobs();
+
+            vault.HostFilter.ShouldBe("pro");
+            rebuilds.ShouldBe(1, "only the last letter's wait passes the text on");
+            vault.VisibleHosts.ShouldHaveSingleItem().Label.ShouldBe("prod-db");
+        });
+    }
+
     // ---- Helpers ----
 
     private static void RightClick(Visual card, Visual window)