feat(runtime): own character selection flow

src/AcDream.Runtime/GameRuntimeCommands.cs

@@ -35,6 +35,7 @@ public enum RuntimeSessionStartStatus
     /// exit-code mapping, not a failure.
     /// </summary>
     ProbeComplete,
+    AwaitingCharacterSelection,
 }
 
 public readonly record struct RuntimeSessionStartResult(
@@ -381,6 +382,10 @@ public interface IGameRuntimeCommands
 {
     IRuntimeSessionCommands Session { get; }
 
+    Session.IRuntimeCharacterSelectionCommands CharacterSelection =>
+        throw new NotSupportedException(
+            "This command adapter does not project character selection.");
+
     IRuntimeSelectionCommands Selection { get; }
 
     IRuntimeCombatCommands Combat { get; }