fix(central-ui): Sites page re-check no longer holds the deploy controls; pluralise; clear stale caption on error

The forced refresh after a successful Deploy Artifacts ran inside the try, so
the Bulk-actions toggle and every per-site Deploy item stayed disabled for a
whole fleet evaluation after the success toast; it now runs after the finally,
behind a re-render, with the Re-check spinner showing it in flight. Also:
pluralise the instance line's noun, drop a stale "as of" caption when a
re-check faults, skip the fleet evaluation when the site load itself failed,
and render the badge tooltip through UtcDateTime so the UTC label is honest.

Claude-Session: https://claude.ai/code/session_01Y5ef34iUUMjmwnMpL9xgmB

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/Sites.razor

@@ -242,6 +242,10 @@
         }
         _loading = false;
 
+        // Nothing to badge: the page is showing an error banner, not a card grid, so a
+        // whole-fleet flatten would buy nothing.
+        if (_errorMessage != null) return;
+
         // Render the cards now — the pending-updates evaluation below is a whole-fleet
         // flatten and must never hold the list behind it.
         StateHasChanged();
@@ -268,6 +272,10 @@
         }
         catch (Exception ex)
         {
+            // The error wins over whatever a previous evaluation said: a failed re-check
+            // must not leave a stale "as of" caption standing next to unavailable badges.
+            _updates = null;
+            _updatesBySite = new Dictionary<int, SitePendingUpdates>();
             _updatesError = ex.Message;
             Logger.LogWarning(ex, "Pending-updates evaluation failed; Sites page badges show unavailable.");
         }
@@ -301,6 +309,7 @@
 
     private async Task DeployArtifacts(Site site)
     {
+        var succeeded = false;
         _deploying = true;
         try
         {
@@ -308,12 +317,9 @@
             var result = await ArtifactDeploymentService.RetryForSiteAsync(
                 site.Id, site.SiteIdentifier, user);
 
-            if (result.IsSuccess)
+            succeeded = result.IsSuccess;
-            {
+            if (succeeded)
                 _toast.ShowSuccess($"Artifacts deployed to '{site.Name}'.");
-                // Force a re-evaluation so the badge flips to current immediately.
-                await LoadUpdatesAsync(force: true);
-            }
             else
                 _toast.ShowError($"Deploy to '{site.Name}' failed: {result.Error}");
         }
@@ -325,23 +331,32 @@
         {
             _deploying = false;
         }
+
+        if (succeeded)
+        {
+            // Re-enable the deploy controls FIRST: the forced re-evaluation is a whole-fleet
+            // flatten, and the operator should not sit behind it once the deploy has landed.
+            // Its own progress shows on the Re-check button's spinner.
+            StateHasChanged();
+            await LoadUpdatesAsync(force: true);
+        }
     }
 
     private async Task DeployArtifactsToAllSites()
     {
+        var succeeded = false;
         _deploying = true;
         try
         {
             var user = await GetCurrentUserAsync();
             var result = await ArtifactDeploymentService.DeployToAllSitesAsync(user);
 
-            if (result.IsSuccess)
+            succeeded = result.IsSuccess;
+            if (succeeded)
             {
                 var summary = result.Value!;
                 _toast.ShowSuccess(
                     $"Artifacts deployed: {summary.SuccessCount} succeeded, {summary.FailureCount} failed.");
-                // Force a re-evaluation so the badges flip to current immediately.
-                await LoadUpdatesAsync(force: true);
             }
             else
             {
@@ -356,6 +371,13 @@
         {
             _deploying = false;
         }
+
+        if (succeeded)
+        {
+            // Re-enable the deploy controls FIRST — see DeployArtifacts.
+            StateHasChanged();
+            await LoadUpdatesAsync(force: true);
+        }
     }
 
     // Per-site Artifacts badge. Bootstrap .badge markup, matching the Topology page's
@@ -381,7 +403,7 @@
                     break;
                 case ArtifactDeploymentState.OutOfDate:
                     <span class="badge bg-warning text-dark ms-2"
-                          title="@(u.ArtifactsDeployedAt is { } at ? $"Artifacts last deployed {at.ToString("u")}" : null)"
+                          title="@(u.ArtifactsDeployedAt is { } at ? $"Artifacts last deployed {at.UtcDateTime.ToString("yyyy-MM-dd HH:mm:ss")} UTC" : null)"
                           aria-label="Artifacts: out of date"><i class="bi bi-exclamation-triangle me-1"></i>Artifacts out of date</span>
                     break;
                 case ArtifactDeploymentState.NeverDeployed:
@@ -396,9 +418,11 @@
     // the rendered text stays contiguous (Razor would interleave layout whitespace).
     private static string InstanceSummary(SitePendingUpdates u)
     {
+        var noun = u.DeployedInstanceCount == 1 ? "instance" : "instances";
+
         var text = u.StaleInstanceCount == 0
-            ? $"All {u.DeployedInstanceCount} instances current"
+            ? $"All {u.DeployedInstanceCount} {noun} current"
-            : $"{u.StaleInstanceCount} of {u.DeployedInstanceCount} instances out of date";
+            : $"{u.StaleInstanceCount} of {u.DeployedInstanceCount} {noun} out of date";
 
         if (u.UnknownInstanceCount > 0)
         {

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Admin/SitesPageTests.cs

@@ -179,6 +179,27 @@ public class SitesPageTests : BunitContext
         });
     }
 
+    [Fact]
+    public void InstanceLine_PluralisesTheSingleInstanceCase()
+    {
+        RegisterServices();
+        _siteRepo.GetAllSitesAsync().Returns(Sites(1, 2));
+        _siteRepo.GetAllDataConnectionsAsync().Returns(new List<DataConnection>());
+        _pendingUpdates.GetAsync(Arg.Any<bool>(), Arg.Any<CancellationToken>())
+            .Returns(_ => Task.FromResult(Snapshot(
+                Pending(1, ArtifactDeploymentState.Current, deployed: 1, stale: 1),
+                Pending(2, ArtifactDeploymentState.Current, deployed: 1))));
+
+        var cut = Render<SitesPage>();
+
+        cut.WaitForAssertion(() =>
+        {
+            Assert.Contains("1 of 1 instance out of date", cut.Markup);
+            Assert.Contains("All 1 instance current", cut.Markup);
+            Assert.DoesNotContain("1 instances", cut.Markup);
+        });
+    }
+
     [Fact]
     public void Recheck_ForcesRefresh()
     {
@@ -193,6 +214,46 @@ public class SitesPageTests : BunitContext
             _pendingUpdates.Received().GetAsync(true, Arg.Any<CancellationToken>()));
     }
 
+    [Fact]
+    public void SiteLoadFailure_SkipsTheFleetEvaluation()
+    {
+        RegisterServices();
+        _siteRepo.GetAllSitesAsync()
+            .Returns<Task<IReadOnlyList<Site>>>(_ => throw new InvalidOperationException("db down"));
+
+        var cut = Render<SitesPage>();
+
+        cut.WaitForAssertion(() => Assert.Contains("Failed to load sites", cut.Markup));
+        // No cards to badge, so the whole-fleet flatten must not run at all.
+        _pendingUpdates.DidNotReceive().GetAsync(Arg.Any<bool>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public void FailedRecheck_ClearsTheStaleAsOfCaption()
+    {
+        RegisterServices();
+        _siteRepo.GetAllSitesAsync().Returns(Sites(1));
+        _siteRepo.GetAllDataConnectionsAsync().Returns(new List<DataConnection>());
+        _pendingUpdates.GetAsync(Arg.Any<bool>(), Arg.Any<CancellationToken>())
+            .Returns(_ => Task.FromResult(Snapshot(Pending(1, ArtifactDeploymentState.Current))));
+
+        var cut = Render<SitesPage>();
+        cut.WaitForAssertion(() => Assert.Contains("Updates as of", cut.Markup));
+
+        // The re-check now faults: the error wins, so the caption from the earlier good
+        // evaluation must not stand next to "unavailable" badges.
+        _pendingUpdates.GetAsync(Arg.Any<bool>(), Arg.Any<CancellationToken>())
+            .Returns<Task<PendingUpdatesSnapshot>>(_ => throw new InvalidOperationException("evaluator down"));
+        cut.Find("button[aria-label=\"Re-check pending updates\"]").Click();
+
+        cut.WaitForAssertion(() =>
+        {
+            Assert.DoesNotContain("Updates as of", cut.Markup);
+            Assert.Contains("Artifacts: unavailable", cut.Markup);
+            Assert.Contains("Site1", cut.Markup);
+        });
+    }
+
     [Fact]
     public void CacheFault_ShowsUnavailable_AndSitesStillRender()
     {