feat(runtime): own character selection flow

src/AcDream.Runtime/Session/LiveSessionContracts.cs

@@ -29,7 +29,14 @@ public sealed record LiveSessionConnectOptions(
     /// itself does not enforce that pairing — the headless config loader
     /// does, before a <see cref="LiveSessionConnectOptions"/> is ever built.
     /// </summary>
-    bool Probe = false);
+    bool Probe = false,
+    /// <summary>
+    /// Keep the connected transport in Runtime's pre-world selection state
+    /// instead of applying the legacy first-available fallback. Graphical
+    /// composition enables this only when no explicit selector was supplied;
+    /// direct/headless callers retain the existing default behavior.
+    /// </summary>
+    bool AwaitCharacterSelection = false);
 
 public interface IRuntimeLiveSessionFramePhase
 {