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>

packages/application/src/index.ts

@@ -4,5 +4,6 @@ export { advanceTurnUseCase } from "./advance-turn-use-case.js";
 export { editCombatantUseCase } from "./edit-combatant-use-case.js";
 export type { EncounterStore } from "./ports.js";
 export { removeCombatantUseCase } from "./remove-combatant-use-case.js";
+export { retreatTurnUseCase } from "./retreat-turn-use-case.js";
 export { setHpUseCase } from "./set-hp-use-case.js";
 export { setInitiativeUseCase } from "./set-initiative-use-case.js";

packages/application/src/retreat-turn-use-case.ts

@@ -0,0 +1,21 @@
+import {
+	type DomainError,
+	type DomainEvent,
+	isDomainError,
+	retreatTurn,
+} from "@initiative/domain";
+import type { EncounterStore } from "./ports.js";
+
+export function retreatTurnUseCase(
+	store: EncounterStore,
+): DomainEvent[] | DomainError {
+	const encounter = store.get();
+	const result = retreatTurn(encounter);
+
+	if (isDomainError(result)) {
+		return result;
+	}
+
+	store.save(result.encounter);
+	return result.events;
+}