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/Settings/RuntimeSettingsControllerTests.cs

@@ -524,6 +524,27 @@ public sealed class RuntimeSettingsControllerTests
         Assert.Equal(1, second.UiLockCalls);
     }
 
+    [Fact]
+    public void OwnedRuntimeTargetsReleaseExactlyAndAllowRebind()
+    {
+        var events = new List<string>();
+        RuntimeSettingsController controller = CreateController(events: events);
+        var first = new FakeRuntimeTargets(events);
+        var second = new FakeRuntimeTargets(events);
+
+        IDisposable firstBinding = controller.BindRuntimeTargetsOwned(first);
+        Assert.Throws<InvalidOperationException>(() =>
+            controller.BindRuntimeTargetsOwned(second));
+
+        firstBinding.Dispose();
+        using IDisposable secondBinding = controller.BindRuntimeTargetsOwned(second);
+        firstBinding.Dispose();
+        controller.SetUiLocked(true);
+
+        Assert.Equal(0, first.UiLockCalls);
+        Assert.Equal(1, second.UiLockCalls);
+    }
+
     [Fact]
     public void DisplayPersistenceFailureDoesNotPublishStateOrTargets()
     {