fix(diag): gate connected soak on guaranteed login boundary

The first-player-position line is emitted only when initial streaming must recenter. Treating it as a required login event made a valid same-landblock login time out while route automation was already running. Gate on in-world and the route's authoritative materialization barriers instead.

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

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

@@ -344,6 +344,28 @@ public sealed class ConnectedR6SoakContractTests
             StringComparison.Ordinal);
     }
 
+    [Fact]
+    public void LoginGateDoesNotRequireTheOptionalFirstPositionRecenterDiagnostic()
+    {
+        string source = File.ReadAllText(Path.Combine(
+            FindRepoRoot(),
+            "tools",
+            "run-connected-r6-soak.ps1"));
+
+        Assert.Contains(
+            "Wait-ForLogPattern $process $stdoutLog 'live: in world'",
+            source,
+            StringComparison.Ordinal);
+        Assert.DoesNotContain(
+            "Wait-ForLogPattern $process $stdoutLog 'live: first player position'",
+            source,
+            StringComparison.Ordinal);
+        Assert.Contains(
+            "route materialization below is the deterministic world-ready barrier.",
+            source,
+            StringComparison.Ordinal);
+    }
+
     [Fact]
     public void DenseTownModeUsesTheDedicatedOneCheckpointRoute()
     {

tools/run-connected-r6-soak.ps1

@@ -717,7 +717,10 @@ try {
     }
 
     $null = Wait-ForLogPattern $process $stdoutLog 'live: in world' 1 $LoginTimeoutSeconds
-    $null = Wait-ForLogPattern $process $stdoutLog 'live: first player position' 1 $LoginTimeoutSeconds
+    # "live: first player position" is a recenter diagnostic, not a session
+    # boundary: it is intentionally absent when the player's authoritative
+    # first cell already matches the initial streaming center. The first
+    # route materialization below is the deterministic world-ready barrier.
     Write-Marker ("in-world elapsed={0:N1}s" -f $stopwatch.Elapsed.TotalSeconds)
 
     foreach ($destination in $destinations) {