test(playwright): make EventLogs query-completion deterministic (review fix)

tests/ZB.MOM.WW.ScadaBridge.CentralUI.PlaywrightTests/Monitoring/EventLogsTests.cs

@@ -85,15 +85,24 @@ public class EventLogsTests
         await page.GotoAsync($"{PlaywrightFixture.BaseUrl}{EventLogsUrl}");
         await page.WaitForLoadStateAsync(LoadState.NetworkIdle);
 
-        await page.Locator("#filter-site").SelectOptionAsync(new SelectOptionValue { Value = "site-a" });
-        await page.Locator("button.btn.btn-primary.btn-sm:has-text('Search')").ClickAsync();
+        await Assertions.Expect(page.Locator("h4:has-text('Site Event Logs')")).ToBeVisibleAsync();
 
-        // The query resolved once the results table renders. The empty-state is itself a
-        // <tr><td colspan=7>No events found.</td></tr>, so a data row OR the empty-state
-        // row both surface under table tbody tr. Generous timeout: the fetch is an Akka
-        // Ask round-trip to a live site.
-        var settled = page.Locator("table tbody tr, td:has-text('No events found.')");
-        await Assertions.Expect(settled.First).ToBeVisibleAsync(new() { Timeout = 15_000 });
+        await page.Locator("#filter-site").SelectOptionAsync(new SelectOptionValue { Value = "site-a" });
+        var searchBtn = page.Locator("button.btn.btn-primary.btn-sm:has-text('Search')");
+        await searchBtn.ClickAsync();
+
+        // The Search button re-enables only when _searching flips back to false, i.e. after the
+        // site's Akka Ask round-trip completes. Gating on it here makes the table assertion below a
+        // genuine post-query check (a hung Ask fails here instead of false-passing on the
+        // intermediate empty render Blazor flushes while _entries is a momentary empty list).
+        await Assertions.Expect(searchBtn).ToBeEnabledAsync(new() { Timeout = 15_000 });
+
+        // The query has completed (Search re-enabled above), so the terminal table render is now
+        // present: a data row OR the empty-state row. The empty-state markup is itself a
+        // <tr><td colspan=7>No events found.</td></tr> living inside table tbody, so "table tbody
+        // tr" matches it whether or not the site has events.
+        var settled = page.Locator("table tbody tr");
+        await Assertions.Expect(settled.First).ToBeVisibleAsync(new() { Timeout = 5_000 });
 
         // Exercise the row-expand ONLY IF real data rows exist. A clean site may have zero
         // logged events, and event logs are not seedable from central — so when no expand