fix(diag): attach EventPipe observers after client startup

Starting dotnet-counters in the process-creation race can suspend the CLR before the graphical host creates its window. Wait for the guaranteed in-world boundary, then attach counters and contention tracing during the route's warm-up interval.

Co-Authored-By: Codex <noreply@openai.com>

tests/AcDream.App.Tests/Diagnostics/ConnectedR6SoakContractTests.cs

@@ -351,6 +351,13 @@ public sealed class ConnectedR6SoakContractTests
             "RuntimeCounters = if (-not $SkipRuntimeCounters) { $runtimeCounters } else { $null }",
             source,
             StringComparison.Ordinal);
+        AssertAppearsInOrder(
+            source,
+            "Wait-ForLogPattern $process $stdoutLog 'live: in world'",
+            "if (-not $SkipRuntimeCounters) {",
+            "Start-Process -FilePath 'dotnet-counters'",
+            "if ($CaptureContention) {",
+            "Start-Process -FilePath 'dotnet-trace'");
     }
 
     [Fact]