T012–T016: Phase 3 application + web shell (use case, ports, React hook, UI, README)

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

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

@@ -0,0 +1,47 @@
+import type { EncounterStore } from "@initiative/application";
+import { advanceTurnUseCase } from "@initiative/application";
+import type { DomainEvent, Encounter } from "@initiative/domain";
+import {
+	combatantId,
+	createEncounter,
+	isDomainError,
+} from "@initiative/domain";
+import { useCallback, useRef, useState } from "react";
+
+function createDemoEncounter(): Encounter {
+	const result = createEncounter([
+		{ id: combatantId("1"), name: "Aria" },
+		{ id: combatantId("2"), name: "Brak" },
+		{ id: combatantId("3"), name: "Cael" },
+	]);
+
+	if (isDomainError(result)) {
+		throw new Error(`Failed to create demo encounter: ${result.message}`);
+	}
+
+	return result;
+}
+
+export function useEncounter() {
+	const [encounter, setEncounter] = useState<Encounter>(createDemoEncounter);
+	const [events, setEvents] = useState<DomainEvent[]>([]);
+	const encounterRef = useRef(encounter);
+	encounterRef.current = encounter;
+
+	const advanceTurn = useCallback(() => {
+		const store: EncounterStore = {
+			get: () => encounterRef.current,
+			save: (e) => setEncounter(e),
+		};
+
+		const result = advanceTurnUseCase(store);
+
+		if (isDomainError(result)) {
+			return;
+		}
+
+		setEvents((prev) => [...prev, ...result]);
+	}, []);
+
+	return { encounter, events, advanceTurn } as const;
+}