test(planning): hold the worker until the preparation cancel arrives

The worker reads its queue only between event-loop turns, so the
calendar preparation could finish before the cancel sent on its second
progress update arrived, and the test received a complete plan. Use the
real-worker harness hold already applied to the checkpoint cancellation
test, and cancel on the first preparation update so the hold is released.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/app/services/leave-planner.worker.spec.ts

@@ -587,8 +587,8 @@ parentPort.on('message', (data) => globalThis.self.onmessage({ data }));
 	);
 
 	it('stops during calendar preparation without a plan or an obligation conflict', async () => {
+		holdForCancelAtStage = 'preparation';
 		const stages: string[] = [];
-		let preparationUpdates = 0;
 		const calculation = createPlanningCalculation({
 			horizon: { start: '2024-01-01', end: '2027-01-01' },
 			balances: [],
@@ -596,7 +596,7 @@ parentPort.on('message', (data) => globalThis.self.onmessage({ data }));
 			declaredDays: [{ date: '2024-01-02', type: 'other' }],
 			progress: (stage) => {
 				stages.push(stage);
-				if (stage === 'preparation' && ++preparationUpdates === 2) calculation.cancel();
+				if (stage === 'preparation') calculation.cancel();
 			},
 		});
 		const outcome = await calculation.outcome;
@@ -606,7 +606,7 @@ parentPort.on('message', (data) => globalThis.self.onmessage({ data }));
 		});
 		if (outcome.kind !== 'PlanningIncomplete') return;
 		expect(outcome.incumbent).toBeUndefined();
-		expect(preparationUpdates).toBeGreaterThanOrEqual(2);
+		expect(stages).toContain('preparation');
 		expect(stages).not.toContain('obligations');
 		expect(await calculation.explanationError).toBeUndefined();
 		expect(heartbeats).toBeGreaterThan(0);