refactor(app): compose session and player startup

Move streaming, live-session, hydration, local-player, combat, and teleport construction behind the typed Phase-7 boundary. Add exact-owner runtime bindings and focused spawn-claim classification so partial startup rolls back without retaining old session targets while preserving the accepted construction and frame dependencies.

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

tests/AcDream.App.Tests/Rendering/DevToolsFramePresenterTests.cs

@@ -1,6 +1,7 @@
 using System.Numerics;
 using System.Reflection;
 using AcDream.App.Diagnostics;
+using AcDream.App.Net;
 using AcDream.App.Rendering;
 using AcDream.UI.Abstractions;
 
@@ -8,6 +9,24 @@ namespace AcDream.App.Tests.Rendering;
 
 public sealed class DevToolsFramePresenterTests
 {
+    [Fact]
+    public void CommandBusOwnedBindingReleasesExactlyAndAllowsRebind()
+    {
+        var source = new DevToolsCommandBusSource();
+        using var first = new LiveSessionController();
+        using var second = new LiveSessionController();
+
+        IDisposable firstBinding = source.BindOwned(first);
+        Assert.Same(first.Commands, source.Current);
+        Assert.Throws<InvalidOperationException>(() => source.BindOwned(second));
+
+        firstBinding.Dispose();
+        using IDisposable secondBinding = source.BindOwned(second);
+        firstBinding.Dispose();
+
+        Assert.Same(second.Commands, source.Current);
+    }
+
     [Fact]
     public void Frame_PreservesBeginThenMenuPanelsAndDrawDataOrder()
     {