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>

src/AcDream.App/UI/CursorFeedbackController.cs

@@ -1,4 +1,5 @@
 using AcDream.Core.Combat;
+using AcDream.Runtime.Gameplay;
 
 namespace AcDream.App.UI;
 

src/AcDream.App/UI/InteractionState.cs

@@ -1,79 +0,0 @@
-namespace AcDream.App.UI;
-
-public enum InteractionModeKind
-{
-    None,
-    Use,
-    Examine,
-    UseItemOnTarget,
-}
-
-public readonly record struct InteractionMode(
-    InteractionModeKind Kind,
-    uint SourceObjectId = 0)
-{
-    public static InteractionMode None => new(InteractionModeKind.None);
-}
-
-public readonly record struct InteractionModeTransition(
-    InteractionMode Previous,
-    InteractionMode Current);
-
-/// <summary>
-/// Single App-layer owner for retail's pointer interaction mode. Core selection
-/// remains session truth; this state represents temporary UI orchestration.
-/// </summary>
-public sealed class InteractionState
-{
-    public InteractionMode Current { get; private set; } = InteractionMode.None;
-
-    public event Action<InteractionModeTransition>? Changed;
-
-    public bool EnterUse() => Set(new InteractionMode(InteractionModeKind.Use));
-
-    public bool EnterExamine() => Set(new InteractionMode(InteractionModeKind.Examine));
-
-    public bool EnterUseItemOnTarget(uint sourceObjectId)
-    {
-        if (sourceObjectId == 0)
-            throw new ArgumentOutOfRangeException(nameof(sourceObjectId));
-        return Set(new InteractionMode(InteractionModeKind.UseItemOnTarget, sourceObjectId));
-    }
-
-    public bool Clear() => Set(InteractionMode.None);
-
-    /// <summary>
-    /// Publishes the session-reset edge even when the mode is already clear so
-    /// a retry can repair any observer that missed an earlier notification.
-    /// </summary>
-    public void ResetSession()
-    {
-        InteractionMode previous = Current;
-        Current = InteractionMode.None;
-        Action<InteractionModeTransition>? listeners = Changed;
-        if (listeners is null)
-            return;
-
-        var transition = new InteractionModeTransition(previous, InteractionMode.None);
-        List<Exception>? failures = null;
-        foreach (Action<InteractionModeTransition> listener in listeners.GetInvocationList())
-        {
-            try { listener(transition); }
-            catch (Exception error) { (failures ??= []).Add(error); }
-        }
-        if (failures is not null)
-            throw new AggregateException(
-                "One or more interaction-mode reset observers failed.",
-                failures);
-    }
-
-    private bool Set(InteractionMode mode)
-    {
-        if (Current == mode)
-            return false;
-        InteractionMode previous = Current;
-        Current = mode;
-        Changed?.Invoke(new InteractionModeTransition(previous, mode));
-        return true;
-    }
-}

src/AcDream.App/UI/ItemInteractionController.cs

@@ -1,6 +1,7 @@
 using System;
 using AcDream.Core.Combat;
 using AcDream.Core.Items;
+using AcDream.Runtime.Gameplay;
 
 namespace AcDream.App.UI;
 
@@ -74,6 +75,7 @@ public sealed class ItemInteractionController : IDisposable
     public ItemInteractionController(
         ClientObjectTable objects,
         InventoryTransactionState transactions,
+        InteractionState interactionState,
         Func<uint> playerGuid,
         Action<uint>? sendUse,
         Action<uint, uint>? sendUseWithTarget,
@@ -82,7 +84,6 @@ public sealed class ItemInteractionController : IDisposable
         Action<uint>? sendExamine = null,
         Func<long>? nowMs = null,
         Action<string>? toast = null,
-        InteractionState? interactionState = null,
         Func<bool>? readyForInventoryRequest = null,
         Func<uint>? activeVendorId = null,
         Func<uint>? groundObjectId = null,
@@ -133,7 +134,8 @@ public sealed class ItemInteractionController : IDisposable
         _dragOnPlayerOpensSecureTrade = dragOnPlayerOpensSecureTrade ?? (() => true);
         _systemMessage = systemMessage;
         _requestUse = requestUse;
-        _interactionState = interactionState ?? new InteractionState();
+        _interactionState = interactionState
+            ?? throw new ArgumentNullException(nameof(interactionState));
         _transactions = transactions
             ?? throw new ArgumentNullException(nameof(transactions));
         if (!ReferenceEquals(_transactions.Objects, _objects))