fix(centralui): stabilise Site Calls + Audit grid Playwright E2E

Three Playwright E2E failures, all test-side timing/data bugs (no
feature defects found):

- AuditGridColumnTests.ColumnOrderAndWidths_PersistAcrossReload: read
  sessionStorage synchronously right after Mouse.UpAsync, racing the
  async OnColumnResized/OnColumnReordered JS->.NET->JS save round-trip.
  Now polls (WaitForFunctionAsync) for the storage keys and for the
  reorder re-render to settle; also hardens the flaky ReorderDrag test.

- SiteCallsPageTests.FilterNarrowing_ChannelFilterShrinksGrid: the
  Target-keyword #sc-search @bind committed via the Query click's own
  blur, racing change vs click on the circuit so Search() sometimes
  ran with a stale empty filter. Commit the value with an explicit,
  fully-awaited DispatchEventAsync('change') and use the retrying
  ToHaveCount assertion for the negative row checks.

- SiteCallsPageTests.RetryClickThrough_OnParkedRow: seeded SourceSite
  'plant-a' is not a real cluster site (site-a/b/c), so the relay had
  no ClusterClient route and only resolved on the 10s inner Ask
  timeout - past the 5s toast wait. Seed a live site (site-a) for a
  fast NotParked round-trip and give the toast a 15s wait.

Playwright E2E suite: 60 passed, 0 failed, 0 skipped.

tests/ScadaLink.CentralUI.PlaywrightTests/Audit/AuditGridColumnTests.cs

@@ -83,6 +83,36 @@ public class AuditGridColumnTests
             .EvaluateAllAsync<string[]>("els => els.map(e => e.getAttribute('data-col-key'))");
     }
 
+    /// <summary>
+    /// Polls until <paramref name="storageKey"/> has been written to
+    /// <c>sessionStorage</c>. The grid persists a resize/reorder
+    /// asynchronously — the browser-side drag fires a fire-and-forget
+    /// JS→.NET invoke (<c>OnColumnResized</c>/<c>OnColumnReordered</c>), and
+    /// the .NET handler then round-trips back through JS interop to write
+    /// <c>sessionStorage</c>. A bare <c>getItem</c> immediately after the drag
+    /// races that round-trip; this waits for the key to actually land.
+    /// </summary>
+    private static async Task WaitForStorageKeyAsync(IPage page, string storageKey)
+    {
+        await page.WaitForFunctionAsync(
+            "key => sessionStorage.getItem(key) !== null", storageKey);
+    }
+
+    /// <summary>
+    /// Polls until the header's first column key equals <paramref name="expectedFirstKey"/>.
+    /// A drag-to-reorder re-renders the header asynchronously (the JS→.NET
+    /// <c>OnColumnReordered</c> invoke is fire-and-forget), so reading the
+    /// header order synchronously after <c>DragToAsync</c> can observe the
+    /// pre-reorder layout. This waits for the re-render to settle.
+    /// </summary>
+    private static async Task WaitForFirstColumnAsync(IPage page, string expectedFirstKey)
+    {
+        await page.WaitForFunctionAsync(
+            "key => { var th = document.querySelector('thead th[data-col-key]'); " +
+            "return th && th.getAttribute('data-col-key') === key; }",
+            expectedFirstKey);
+    }
+
     [SkippableFact]
     public async Task ResizeHandle_DraggingWidensColumn_AndSurvivesReload()
     {
@@ -156,18 +186,22 @@ public class AuditGridColumnTests
             var source = page.Locator("[data-col-key='Status']");
             var target = page.Locator("[data-col-key='OccurredAtUtc']");
             await source.DragToAsync(target);
-            await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
+            // The reorder re-renders the header asynchronously (fire-and-forget
+            // JS→.NET invoke); wait for it to settle before reading the order.
+            await WaitForFirstColumnAsync(page, "Status");
 
             var afterOrder = await HeaderOrderAsync(page);
             Assert.Equal("Status", afterOrder[0]);
             Assert.True(afterOrder.ToList().IndexOf("Status") < afterOrder.ToList().IndexOf("OccurredAtUtc"),
                 "Expected Status to be reordered ahead of OccurredAtUtc.");
 
-            // Reload: the persisted order is restored from sessionStorage.
+            // Reload: the persisted order is restored from sessionStorage on
+            // the grid's first render — wait for the header to reflect it.
             await page.ReloadAsync();
             await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
             await page.Locator("[data-test='filter-apply']").ClickAsync();
             await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
+            await WaitForFirstColumnAsync(page, "Status");
 
             var afterReload = await HeaderOrderAsync(page);
             Assert.Equal("Status", afterReload[0]);
@@ -194,7 +228,10 @@ public class AuditGridColumnTests
             // Reorder then resize, then confirm sessionStorage carries both.
             await page.Locator("[data-col-key='Status']")
                 .DragToAsync(page.Locator("[data-col-key='OccurredAtUtc']"));
-            await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
+            // Wait for the reorder re-render to settle before measuring the
+            // resize handle, so the handle's bounding box is read off the
+            // post-reorder layout.
+            await WaitForFirstColumnAsync(page, "Status");
 
             var handle = page.Locator("[data-test='col-resize-Target']");
             var handleBox = await handle.BoundingBoxAsync();
@@ -206,7 +243,15 @@ public class AuditGridColumnTests
             await page.Mouse.MoveAsync(startX + 90, startY, new MouseMoveOptions { Steps = 6 });
             await page.Mouse.UpAsync();
 
-            // Both keys are written under the auditGrid: namespace.
+            // Both keys are written under the auditGrid: namespace — but the
+            // write is asynchronous: pointer-up fires a fire-and-forget
+            // OnColumnResized/OnColumnReordered JS→.NET invoke, and the .NET
+            // handler then round-trips back through JS interop to call
+            // auditGrid.save. Reading sessionStorage synchronously right after
+            // Mouse.UpAsync races that round-trip, so poll for both keys to
+            // land before asserting on them.
+            await WaitForStorageKeyAsync(page, "auditGrid:columnOrder");
+            await WaitForStorageKeyAsync(page, "auditGrid:columnWidths");
             var orderJson = await page.EvaluateAsync<string?>(
                 "() => sessionStorage.getItem('auditGrid:columnOrder')");
             var widthsJson = await page.EvaluateAsync<string?>(
@@ -216,11 +261,14 @@ public class AuditGridColumnTests
             Assert.NotNull(widthsJson);
             Assert.Contains("Target", widthsJson!);
 
-            // After a reload the restored grid reflects the stored order.
+            // After a reload the restored grid reflects the stored order. The
+            // restore happens on the grid's first render (LoadPersistedState →
+            // StateHasChanged), so wait for the header to reflect it.
             await page.ReloadAsync();
             await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
             await page.Locator("[data-test='filter-apply']").ClickAsync();
             await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
+            await WaitForFirstColumnAsync(page, "Status");
 
             var restoredOrder = await HeaderOrderAsync(page);
             Assert.Equal("Status", restoredOrder[0]);