Merge campaign-launcher-406: fix #406 — truthful client exit self-report + bounded stderr capture

The crashed-client 'graceful' status line was the CLIENT's own Dispose-path
self-report, not the launcher's observation; Run() now latches the escaping
failure and the shutdown report writes reason:'crashed'. Sessions also gain
a bounded client.err.log beside status.jsonl on both spawn paths.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -137,6 +137,14 @@ public sealed class GameWindow :
         _constructionCleanup = new();
     private readonly AcDream.App.World.WorldEnvironmentController _worldEnvironment;
     private readonly GameWindowLifetime _lifetime = new();
+    // fix #406: set by Run()'s own catch the instant an exception escapes
+    // the Silk.NET frame loop, BEFORE it is rethrown and unwinds through
+    // Program.cs's `using var window = ...` (which calls Dispose() —
+    // therefore CompleteShutdown() — while that exception is still in
+    // flight). CompleteShutdown consults this so a crash is never reported
+    // as the hardcoded "exited{code:0,reason:graceful}" the resource
+    // teardown transaction's own convergence would otherwise imply.
+    private Exception? _runFailure;
     private readonly DisplayFramePacingController _displayFramePacing;
     private readonly RuntimeSettingsController _runtimeSettings;
 
@@ -820,6 +828,10 @@ public sealed class GameWindow :
         catch (Exception failure)
         {
             _constructionCleanup.RetainFrom(failure);
+            // fix #406: latch BEFORE rethrowing — Dispose() (and therefore
+            // CompleteShutdown) can run mid-unwind of this exact exception,
+            // via Program.cs's `using var window = ...`.
+            _runFailure = failure;
             throw;
         }
     }
@@ -1698,7 +1710,7 @@ public sealed class GameWindow :
             // OnClosing() native-window-close-request pass) represents the
             // process actually being done.
             if (releaseNativeWindow)
-                _statusWriter.Exited(_options.SessionId ?? "app", 0, "graceful");
+                ReportExited(report);
             return;
         }
 
@@ -1715,12 +1727,41 @@ public sealed class GameWindow :
             Console.Error.WriteLine($"[shutdown] {report.Error}");
 
         if (releaseNativeWindow)
+            ReportExited(report);
+    }
+
+    /// <summary>
+    /// Writes the ONE terminal "exited" status event for this session
+    /// (fix #406). A resource-shutdown transaction can converge cleanly
+    /// (<paramref name="report"/>'s own <see cref="GameWindowLifetimeReport.Status"/>
+    /// says nothing about this) even though this <see cref="Dispose"/> call
+    /// is running mid-unwind of an exception that escaped
+    /// <see cref="Run"/>'s frame loop and is about to terminate the process
+    /// via the CLR's unhandled-exception path — <see cref="_runFailure"/>
+    /// is the one signal that actually distinguishes those two cases.
+    /// Before this fix every such crash wrote the exact same
+    /// "exited{code:0,reason:graceful}" as a real graceful shutdown,
+    /// sending any launcher-side diagnosis in the wrong direction (#406).
+    /// </summary>
+    private void ReportExited(GameWindowLifetimeReport report)
+    {
+        string sessionId = _options.SessionId ?? "app";
+        if (_runFailure is not null)
         {
-            _statusWriter.Exited(
-                _options.SessionId ?? "app",
-                1,
-                "shutdown-incomplete");
+            // The real OS-level exit code (e.g. 0xE0434352 on Windows for
+            // an unhandled .NET exception) is produced by the runtime AFTER
+            // this method returns and the exception keeps propagating — it
+            // cannot be predicted from here. "crashed" is the truthful,
+            // platform-independent classification; the launcher's own
+            // process supervisor observes the real OS exit code separately.
+            _statusWriter.Exited(sessionId, 1, "crashed");
+            return;
         }
+
+        if (report.Status == GameWindowLifetimeStatus.Complete)
+            _statusWriter.Exited(sessionId, 0, "graceful");
+        else
+            _statusWriter.Exited(sessionId, 1, "shutdown-incomplete");
     }
 
     private GameWindowShutdownRoots CaptureShutdownRoots() => new(