test: revert Core.Net serialization; widen the virtual-clock harness patience instead

Serializing AcDream.Core.Net.Tests to fix a Linux starvation REGRESSED Windows,
which had been green: Core.Net went from 1000 passed in 7 s (run 154) to
999/1000 in 17 s (run 155), taking down LossSoak_TwoPercentBidirectional_
ZeroMessageLoss_LedgersConverge, a test that had never failed. That trade trans-
ferred the flake between platforms rather than fixing anything, so it is
reverted: no xunit.runner.json, no csproj change.

The actual fragility is narrower than it looked — exactly ONE test uses
real-time waits (PausedSelector_SeededDroppedServerReady_RecoversOnIdleSweep),
and its harness drives a VIRTUAL clock while asserting on 2 s wall-clock
windows. Those windows are patience for background work, not part of the
assertion, and 2 s only ever encoded 'the machine is idle'. They now share a
60 s HarnessPatience constant.

Nothing about what the test verifies changes: recovery must still occur, a
genuine failure to NAK still fails, and a real hang is still bounded. Campaign N
transport code is untouched.

Local: 1000/1000 in 6 s under the gate filter.

tests/AcDream.Core.Net.Tests/AcDream.Core.Net.Tests.csproj

@@ -22,15 +22,4 @@
     <ProjectReference Include="..\..\src\AcDream.Core.Net\AcDream.Core.Net.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <!-- Several transport tests drive a virtual clock but assert on REAL-time
-         waits (2 s SpinUntil windows). Under default parallelism on a small CI
-         container PausedSelector_SeededDroppedServerReady_RecoversOnIdleSweep
-         took 37-42 s and missed its window, while passing 5/5 in ~350 ms in
-         isolation on the same machine. Serialize the assembly rather than
-         loosen a Campaign N transport assertion. Same settings
-         AcDream.Core.Tests and AcDream.Launcher.Tests already use. -->
-    <None Update="xunit.runner.json" CopyToOutputDirectory="PreserveNewest" />
-  </ItemGroup>
-
 </Project>

tests/AcDream.Core.Net.Tests/Transport/FakeAceTransportTests.cs

@@ -14,6 +14,13 @@ namespace AcDream.Core.Net.Tests.Transport;
 /// </summary>
 public sealed class FakeAceTransportTests
 {
+    /// <summary>
+    /// Wall-clock allowance for background transport work in these
+    /// virtual-clock harnesses. Generous on purpose: it bounds a hang without
+    /// encoding an assumption that the machine is idle.
+    /// </summary>
+    private static readonly TimeSpan HarnessPatience = TimeSpan.FromSeconds(60);
+
     // ---- LossyLink ----
 
     [Fact]
@@ -212,7 +219,14 @@ public sealed class FakeAceTransportTests
 
             Task gapDriver = Task.Run(() =>
             {
-                Assert.True(enterRequest.Wait(TimeSpan.FromSeconds(2)));
+                // These two windows are wall-clock patience for a harness whose
+                // CLOCK is virtual, not part of what the test verifies. Two
+                // seconds was enough on an idle dev box but not on a loaded CI
+                // runner, where this test took 37-42 s and failed while passing
+                // 5/5 in ~350 ms in isolation. Widening the window changes no
+                // assertion — recovery must still happen, and a genuine failure
+                // to NAK still fails the test, just later.
+                Assert.True(enterRequest.Wait(HarnessPatience));
                 // This later sequenced packet passes the seeded loss gate,
                 // exposing the missing ServerReady and parking behind it.
                 fake.EnqueueServerGameMessage(
@@ -220,7 +234,7 @@ public sealed class FakeAceTransportTests
                     GameMessageGroup.UIQueue);
                 Assert.True(SpinWait.SpinUntil(
                     () => session.Transport?.Inbound.NakCount > 0,
-                    TimeSpan.FromSeconds(2)));
+                    HarnessPatience));
 
                 // No datagram follows this virtual-time edge. Recovery now
                 // requires paused EnterWorld's independent periodic sweep.

tests/AcDream.Core.Net.Tests/xunit.runner.json

@@ -1,6 +0,0 @@
-{
-  "$schema": "https://xunit.net/schema/current/xunit.runner.schema.json",
-  "parallelizeAssembly": false,
-  "parallelizeTestCollections": false,
-  "maxParallelThreads": 1
-}