Implement the 012-turn-navigation feature that adds a RetreatTurn domain operation and relocates turn controls to a navigation bar at the top of the encounter tracker

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/hooks/use-encounter.ts

@@ -5,6 +5,7 @@ import {
 	advanceTurnUseCase,
 	editCombatantUseCase,
 	removeCombatantUseCase,
+	retreatTurnUseCase,
 	setHpUseCase,
 	setInitiativeUseCase,
 } from "@initiative/application";
@@ -79,6 +80,16 @@ export function useEncounter() {
 		setEvents((prev) => [...prev, ...result]);
 	}, [makeStore]);
 
+	const retreatTurn = useCallback(() => {
+		const result = retreatTurnUseCase(makeStore());
+
+		if (isDomainError(result)) {
+			return;
+		}
+
+		setEvents((prev) => [...prev, ...result]);
+	}, [makeStore]);
+
 	const nextId = useRef(deriveNextId(encounter));
 
 	const addCombatant = useCallback(
@@ -164,6 +175,7 @@ export function useEncounter() {
 		encounter,
 		events,
 		advanceTurn,
+		retreatTurn,
 		addCombatant,
 		removeCombatant,
 		editCombatant,