fix(combat): persist death and retarget on kill

Keep the velocity-only NPC adaptation inside the locomotion family so authoritative Dead motion remains persistent. Route selection clears through a dedicated combat target controller that reacquires the closest eligible creature when retail Auto Target conditions apply.

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

src/AcDream.Core/Selection/SelectionState.cs

@@ -19,6 +19,7 @@ public enum SelectionChangeReason
     Selected,
     Cleared,
     SelectedObjectRemoved,
+    CombatTargetDied,
     PreviousSelection,
 }