Desktop: stop decrypting the whole keychain on a sync pass that changed nothing

tests/DodoSSH.Client.App.Tests/ShellFlowTests.cs

@@ -656,6 +656,26 @@ public sealed partial class ShellFlowTests : IAsyncLifetime
         vault.IsBusy.ShouldBeFalse("a background pass must never raise the busy flag");
     }
 
+    /// <remarks>
+    /// A pass that moved nothing used to read the whole keychain back anyway — decrypting every item and
+    /// rebuilding every list, once a minute. A rebuilt list has new row objects in it, so the row still being
+    /// the same object is the evidence that nothing was read.
+    /// </remarks>
+    [Fact]
+    public async Task AnAutomaticPassThatMovesNothing_RedrawsNothing()
+    {
+        await UnlockedAsync();
+        var vault = shell.Vault!;
+
+        await AddHostAsync(vault, "prod-db");
+
+        var row = vault.Hosts.ShouldHaveSingleItem();
+
+        await vault.AutoSyncAsync(Token);
+
+        vault.Hosts.ShouldHaveSingleItem().ShouldBeSameAs(row);
+    }
+
     /// <remarks>
     /// The queue has to be arranged by failing the automatic push first. Written the obvious way — add a
     /// host, then call the pass — this test proved nothing at all: saving pushes, so there was no pending