refactor(app): complete session startup composition

Move the live-session reset and routing graph, combat and diagnostic command targets, and the sole gameplay input subscriber into Phase 7 before frame publication. Add exact retryable ownership for late bindings so partial startup cannot strand session or component teardown edges.

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

src/AcDream.App/Combat/LiveCombatModeCommandController.cs

@@ -109,6 +109,24 @@ internal sealed class LiveCombatModeCommandSlot : ILiveCombatModeCommand
         }
     }
 
+    public IDisposable BindOwned(ILiveCombatModeCommand target)
+    {
+        ArgumentNullException.ThrowIfNull(target);
+        lock (_gate)
+        {
+            ObjectDisposedException.ThrowIf(_deactivated, this);
+            if (_target is not null)
+            {
+                throw new InvalidOperationException(
+                    "Live combat-mode commands are already bound.");
+            }
+
+            _target = target;
+        }
+
+        return new Binding(this, target);
+    }
+
     public void Deactivate()
     {
         lock (_gate)
@@ -126,6 +144,23 @@ internal sealed class LiveCombatModeCommandSlot : ILiveCombatModeCommand
                 _target?.Toggle();
         }
     }
+
+    private sealed class Binding : IDisposable
+    {
+        private LiveCombatModeCommandSlot? _owner;
+        private readonly ILiveCombatModeCommand _expected;
+
+        public Binding(
+            LiveCombatModeCommandSlot owner,
+            ILiveCombatModeCommand expected)
+        {
+            _owner = owner;
+            _expected = expected;
+        }
+
+        public void Dispose() =>
+            Interlocked.Exchange(ref _owner, null)?.Unbind(_expected);
+    }
 }
 
 /// <summary>