fix(combat): synchronize auto-target presentation

Make the retained toolbar consume retail's payload-free selection notice from canonical live state so a reentrant Auto Target replacement cannot be erased by the outer clear. Restrict automatic acquisition to the requested hostile non-player monster policy and record the intentional PK edge divergence.

Co-Authored-By: Codex <codex@openai.com>

src/AcDream.Core/Combat/CombatTargetPolicy.cs

@@ -0,0 +1,42 @@
+using AcDream.Core.Items;
+
+namespace AcDream.Core.Combat;
+
+/// <summary>
+/// Eligibility policy for automatic monster acquisition.
+/// </summary>
+public static class CombatTargetPolicy
+{
+    /// <summary>
+    /// Returns true only for a live-data creature that is attackable, is not a
+    /// player, and is not a pet. Friendly NPCs and non-creatures are rejected.
+    /// </summary>
+    /// <remarks>
+    /// The attackability core is retail
+    /// <c>ClientCombatSystem::ObjectIsAttackable @ 0x0056A600</c>. Retail
+    /// <c>AutoTarget @ 0x0056BC80</c> falls back to
+    /// <c>SelectNext(SELECTION_TYPE_COMPASS_ITEM)</c>, whose combat filter also
+    /// uses ObjectIsAttackable. acdream deliberately narrows that set to
+    /// non-player monsters for its automatic acquisition policy; explicit
+    /// player-selection commands remain separate.
+    /// </remarks>
+    public static bool IsHostileMonster(
+        uint playerId,
+        ClientObject? player,
+        ClientObject? candidate)
+    {
+        if (candidate is null
+            || candidate.ObjectId == playerId
+            || (candidate.Type & ItemType.Creature) == 0
+            || (candidate.PublicWeenieBitfield.GetValueOrDefault()
+                & SelectedObjectHealthPolicy.BfPlayer) != 0
+            || candidate.PetOwnerId != 0)
+            return false;
+
+        return SelectedObjectHealthPolicy.ObjectIsAttackable(
+            playerId,
+            player,
+            candidate.ObjectId,
+            candidate);
+    }
+}