refactor(runtime): own canonical action state

Move selection, combat, and interaction target mode under one Runtime owner; make plugins, retained UI, session routing, and typed runtime views borrow its exact children; and add failure-safe reset, instance isolation, source ownership, and normalized checkpoint coverage without changing retail ordering.

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

tests/AcDream.App.Tests/Composition/InteractionRetainedUiCompositionTests.cs

@@ -186,9 +186,8 @@ public sealed class InteractionRetainedUiCompositionTests
                 RetainedInputCapture: null!,
                 InputDispatcher: null,
                 Settings: null!,
-                Combat: null!,
+                Actions: null!,
                 CombatAttackOperations: null!,
-                Selection: null!,
                 Inventory: null!,
                 MagicCatalog: null!,
                 Character: null!,