refactor(runtime): move session lifetime and ordered transport

Move the canonical WorldSession generation, connect/enter/tick/stop transaction, inbound subscription owner, and retryable teardown acknowledgements into AcDream.Runtime. Keep App as a borrowing graphical host with a single inertable command projection and no mirrored session state.

Validated by 79 Runtime tests, 3,776 App tests with three existing skips, the Release solution build, and 8,428 complete Release tests with five existing skips.

Co-authored-by: Codex <codex@openai.com>

src/AcDream.Runtime/Session/LiveSessionLifecycleHost.cs

@@ -0,0 +1,65 @@
+using AcDream.Core.Net;
+
+namespace AcDream.Runtime.Session;
+
+public sealed record LiveSessionLifecycleBindings(
+    Func<WorldSession, LiveSessionBinding> Bind,
+    Action Reset,
+    Action<string, int, string> Connecting,
+    Action Connected,
+    Action<LiveSessionCharacterSelection> Selected,
+    Action<LiveSessionCharacterSelection> Entered);
+
+/// <summary>
+/// Focused adapter between the session lifetime owner and its composition
+/// callbacks. It tracks only the exact borrowed session attached to the host;
+/// domain and presentation state remain behind the supplied callbacks.
+/// </summary>
+public sealed class LiveSessionLifecycleHost : ILiveSessionLifecycleHost
+{
+    private readonly LiveSessionLifecycleBindings _bindings;
+    private WorldSession? _boundSession;
+
+    public LiveSessionLifecycleHost(LiveSessionLifecycleBindings bindings)
+    {
+        _bindings = bindings ?? throw new ArgumentNullException(nameof(bindings));
+        ArgumentNullException.ThrowIfNull(bindings.Bind);
+        ArgumentNullException.ThrowIfNull(bindings.Reset);
+        ArgumentNullException.ThrowIfNull(bindings.Connecting);
+        ArgumentNullException.ThrowIfNull(bindings.Connected);
+        ArgumentNullException.ThrowIfNull(bindings.Selected);
+        ArgumentNullException.ThrowIfNull(bindings.Entered);
+    }
+
+    public LiveSessionBinding BindSession(WorldSession session)
+    {
+        ArgumentNullException.ThrowIfNull(session);
+        if (_boundSession is not null)
+            throw new InvalidOperationException("A live session is already attached to this host.");
+
+        LiveSessionBinding binding = _bindings.Bind(session);
+        _boundSession = session;
+        return binding;
+    }
+
+    public void ResetSessionState() => _bindings.Reset();
+
+    public void ReportConnecting(string host, int port, string user) =>
+        _bindings.Connecting(host, port, user);
+
+    public void ReportConnected() => _bindings.Connected();
+
+    public void ApplySelectedCharacter(LiveSessionCharacterSelection selection) =>
+        _bindings.Selected(selection);
+
+    public void ApplyEnteredWorld(LiveSessionCharacterSelection selection) =>
+        _bindings.Entered(selection);
+
+    public void DetachSession(WorldSession session)
+    {
+        if (!ReferenceEquals(_boundSession, session))
+            throw new InvalidOperationException(
+                "The live-session controller attempted to detach a session that is not bound.");
+        _boundSession = null;
+    }
+}