feat: support extra health state mechanics

src/lib/builder/loadout-combat.test.ts

@@ -164,6 +164,53 @@ describe('loadout mechanic timeline', () => {
 		expect(sprinting.every((event) => event.values?.state === 'sprinting')).toBe(true);
 	});
 
+	it('seeds Extra Health state before periodic stack evaluation', () => {
+		const profile = createDraft().combatProfile;
+		profile.encounterSeconds = 2;
+		profile.extraHealthActive = true;
+		const timeline = buildWeaponMechanicTimeline(
+			{ rpm: 60, magazine: 100, reload_speed: 0 },
+			profile
+		);
+		expect(timeline.filter((event) => event.kind === 'extra_health_changed')).toEqual([{
+			kind: 'extra_health_changed',
+			at: 0,
+			actorId: 'agent',
+			values: { hasExtraHealth: true }
+		}]);
+
+		const program: MechanicProgram = {
+			id: 'extra-health-periodic-stacks',
+			name: 'Extra Health periodic stacks',
+			pools: [
+				{ key: 'active', label: 'Active', scope: 'agent', initial: 0, min: 0, max: 1 },
+				{ key: 'stacks', label: 'Stacks', scope: 'agent', initial: 0, min: 0, max: 10 }
+			],
+			clauses: [{
+				id: 'set-active',
+				when: 'extra_health_changed',
+				if: { kind: 'compare', left: { source: 'event', path: 'values.hasExtraHealth' }, operator: 'eq', right: true },
+				reducer: { kind: 'none' },
+				mutations: [{ kind: 'set', pool: 'active', value: 1 }]
+			}, {
+				id: 'gain-stack',
+				when: 'tick',
+				if: { kind: 'compare', left: { source: 'pool', pool: 'active' }, operator: 'eq', right: 1 },
+				reducer: { kind: 'periodic', intervalSeconds: 1 },
+				mutations: [{ kind: 'add', pool: 'stacks', value: 1 }]
+			}]
+		};
+		const result = evaluateMechanicProgram(program, timeline, {
+			mode: 'custom',
+			encounterSeconds: 2
+		});
+		expect(result.finalState).toEqual(expect.arrayContaining([
+			expect.objectContaining({ pool: 'stacks', value: 2 })
+		]));
+		expect(result.emissions.filter((emission) => emission.clauseId === 'gain-stack')
+			.map((emission) => emission.at)).toEqual([1, 2]);
+	});
+
 	it('falls back to a documented Tier I mechanic when equipment Tier II is absent', () => {
 		const persistedRule = {
 			rule: {