refactor(runtime): compose canonical game runtime root

src/AcDream.Runtime/Gameplay/RuntimeLocalPlayerIdentityState.cs

@@ -0,0 +1,54 @@
+namespace AcDream.Runtime.Gameplay;
+
+public readonly record struct RuntimeLocalPlayerIdentityOwnershipSnapshot(
+    bool IsDisposed,
+    uint ServerGuid,
+    long Revision)
+{
+    public bool IsConverged => IsDisposed && ServerGuid == 0u;
+}
+
+/// <summary>
+/// Canonical session-scoped identity of the local player. Graphical and direct
+/// hosts borrow this exact owner; presentation adapters may not mirror it.
+/// </summary>
+public sealed class RuntimeLocalPlayerIdentityState : IDisposable
+{
+    private uint _serverGuid;
+    private long _revision;
+    private bool _disposed;
+
+    public uint ServerGuid
+    {
+        get => _serverGuid;
+        set
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+            if (_serverGuid == value)
+                return;
+            _serverGuid = value;
+            Interlocked.Increment(ref _revision);
+        }
+    }
+
+    public long Revision => Interlocked.Read(ref _revision);
+    public bool IsDisposed => _disposed;
+
+    public void ResetSession()
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        ServerGuid = 0u;
+    }
+
+    public RuntimeLocalPlayerIdentityOwnershipSnapshot CaptureOwnership() =>
+        new(_disposed, _serverGuid, Revision);
+
+    public void Dispose()
+    {
+        if (_disposed)
+            return;
+        _serverGuid = 0u;
+        Interlocked.Increment(ref _revision);
+        _disposed = true;
+    }
+}