Implement the 009-combatant-hp feature that adds optional max HP and current HP tracking per combatant with +/- controls, direct entry, and persistence

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

packages/application/src/set-hp-use-case.ts

@@ -0,0 +1,24 @@
+import {
+	type CombatantId,
+	type DomainError,
+	type DomainEvent,
+	isDomainError,
+	setHp,
+} from "@initiative/domain";
+import type { EncounterStore } from "./ports.js";
+
+export function setHpUseCase(
+	store: EncounterStore,
+	combatantId: CombatantId,
+	maxHp: number | undefined,
+): DomainEvent[] | DomainError {
+	const encounter = store.get();
+	const result = setHp(encounter, combatantId, maxHp);
+
+	if (isDomainError(result)) {
+		return result;
+	}
+
+	store.save(result.encounter);
+	return result.events;
+}