fix(Core/Combat): Immediately reselect victim after taunt aura update (#25254)

Co-authored-by: blinkysc <blinkysc@users.noreply.github.com>

src/server/game/Combat/ThreatManager.h

@@ -182,6 +182,8 @@ public:
     // Test-only: directly set taunt state on a threat ref
     // Uses uint32 to avoid incomplete-type issue with ThreatReference
     void SetTauntStateForTesting(Unit* target, uint32 state);
+    // Immediately reselect victim (bypasses 1-second Update timer)
+    void UpdateVictimForTesting() { UpdateVictim(); }
 
     ///== REDIRECT SYSTEM ==
     void RegisterRedirectThreat(uint32 spellId, ObjectGuid const& victim, uint32 pct);