fix(centralui): single relay toast, paging/skip polish, extra Site Calls tests

src/ScadaLink.CentralUI/Components/Pages/SiteCalls/SiteCallsReport.razor

@@ -201,6 +201,9 @@
            backwards and the response's NextAfter* cursor to step forwards. *@
         <div class="d-flex justify-content-between align-items-center">
             <span class="text-muted small">
+                @* No "of N" total: keyset paging has no cheap total-count, so
+                   the label is intentionally page-number-only. Do not "fix"
+                   this by adding a total — that would require a COUNT(*). *@
                 Page @(_cursorStack.Count + 1) · @_siteCalls.Count rows
             </span>
             <div>

src/ScadaLink.CentralUI/Components/Pages/SiteCalls/SiteCallsReport.razor.cs

@@ -224,10 +224,20 @@ public partial class SiteCallsReport
     }
 
     /// <summary>
-    /// Surface a relay outcome on the toast. The <see cref="SiteCallRelayOutcome.SiteUnreachable"/>
-    /// case is deliberately distinct from a generic failure — the action was not
-    /// applied but the operator can retry once the site is back online.
+    /// Surface a relay outcome on the toast — exactly one toast per relay
+    /// response. The <see cref="SiteCallRelayOutcome.SiteUnreachable"/> case is
+    /// deliberately distinct from a generic failure: the action was not applied
+    /// but the operator can retry once the site is back online.
     /// </summary>
+    /// <remarks>
+    /// The <see cref="SiteCallRelayOutcome"/> switch is exhaustive, so it owns
+    /// the single toast. <paramref name="siteReachable"/> is a redundant
+    /// cross-check on the same signal (the contract sets it <c>false</c> only
+    /// for <see cref="SiteCallRelayOutcome.SiteUnreachable"/>); it is folded
+    /// INTO the <see cref="SiteCallRelayOutcome.OperationFailed"/> case rather
+    /// than firing a second toast — an <c>OperationFailed</c> response that also
+    /// reports an unreachable site shows the unreachable wording, once.
+    /// </remarks>
     private void ShowRelayOutcome(
         SiteCallRelayOutcome outcome, bool siteReachable, string? errorMessage, string appliedMessage)
     {
@@ -245,19 +255,19 @@ public partial class SiteCallsReport
                     ?? "Site unreachable — the relay did not reach the owning site. "
                        + "Try again once the site is back online.");
                 break;
+            case SiteCallRelayOutcome.OperationFailed when !siteReachable:
+                // An OperationFailed response that nonetheless reports the site
+                // unreachable: trust the reachability signal and show the
+                // unreachable wording instead of the generic failure message.
+                _toast.ShowError(errorMessage
+                    ?? "Site unreachable — the relay did not reach the owning site. "
+                       + "Try again once the site is back online.");
+                break;
             case SiteCallRelayOutcome.OperationFailed:
             default:
                 _toast.ShowError(errorMessage ?? "The site could not apply the action.");
                 break;
         }
-
-        // Defensive: a non-Applied/non-Unreachable outcome that somehow reports an
-        // unreachable site still gets the unreachable wording.
-        if (outcome != SiteCallRelayOutcome.SiteUnreachable && !siteReachable
-            && outcome != SiteCallRelayOutcome.Applied)
-        {
-            _toast.ShowError("Site unreachable — the relay did not reach the owning site.");
-        }
     }
 
     private async Task ShowDetail(SiteCallSummary c)
@@ -353,6 +363,8 @@ public partial class SiteCallsReport
             ? null
             : new DateTimeOffset(DateTime.SpecifyKind(value.Value, DateTimeKind.Utc));
 
+    // A Guid's "N" format is always exactly 32 hex chars, so the [..12] slice is
+    // always in range — no length guard needed.
     private static string ShortId(Guid id) => id.ToString("N")[..12];
 
     private static string StatusBadgeClass(string status) => status switch