refactor(input): own pointer and callback lifetime

Move camera pointer, framebuffer resize, and retained/devtools input edges behind focused reversible owners. Preserve input priority while making shutdown deactivate callbacks before live-session retirement and retry physical detach without stranding transport teardown.

src/AcDream.App/Input/DispatcherMovementInputSource.cs

@@ -31,6 +31,13 @@ internal sealed class DispatcherMovementInputSource : IMovementInputSource
         _dispatcher = dispatcher;
     }
 
+    public void Unbind(InputDispatcher dispatcher)
+    {
+        ArgumentNullException.ThrowIfNull(dispatcher);
+        if (ReferenceEquals(_dispatcher, dispatcher))
+            _dispatcher = null;
+    }
+
     public MovementInput Capture()
     {
         // Devtools owns the whole gameplay keyboard while active, including