fix(assassin): preserve external potion effects

design/user-stories/us-005-use-assassin-abilities.md

@@ -20,6 +20,13 @@ As the **Assassin**, I want stealth and burst mobility so that I can ambush oppo
 - [x] Grounding and supported movement reset jump availability only after the 60-second cooldown has elapsed.
 - [x] Ability cooldowns use unpaused elapsed time and survive death, logout, and restart.
 - [x] The player can inspect remaining cooldowns and receives clear feedback when an activation is unavailable.
+- [x] Tyrant removes only Assassin potion effects that Tyrant itself applied.
+- [x] Invisibility from potions, commands, or other plugins remains active for Assassins and non-Assassins.
+- [x] Tyrant-managed Assassin effects are still removed when abilities expire, roles change, games stop, or the plugin disables.
+
+## Validation
+
+Automated controller tests verify that inactive Tyrant state does not alter ordinary potion effects, active Assassin invisibility is refreshed, and refresh stops at expiry so the short managed effect expires naturally. The complete `./gradlew clean check jar` lifecycle passes.
 
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