feat(09-01): add scheduleOutboxDrain, drainRequested, initOutboxTrigger; route setInterval through wrapper

- Add import { onOutboxDrain } from outboxTrigger.js
- Add let drainRequested = false (D-05 trailing-re-drain flag)
- Export scheduleOutboxDrain(): void — isDraining guard + drainRequested loop (D-05/T-09-01)
  drainRequested=false reset precedes recursive call (Pitfall 3)
  errors caught via .catch to prevent crash (D-02/T-09-03)
- Export initOutboxTrigger(): void — registers onOutboxDrain(() => scheduleOutboxDrain())
- startOutboxWorker setInterval body: scheduleOutboxDrain() replaces runOutboxDrain().catch()
  15 * 1000 interval unchanged (D-08)
- runOutboxDrain body/isDraining guard/finally unchanged (D-02/D-07)
- Fix trigger-wiring tests: add beforeAll(initOutboxTrigger) to wire EventEmitter listener;
  fix Test C mock to return empty rows on trailing drain (correct D-07 behaviour)
- 30/30 outboxWorker tests GREEN; tsc --noEmit clean

apps/api/tests/broker/outboxWorker.test.ts

@@ -13,12 +13,12 @@
  * They will turn GREEN in Plan 03-03 when the implementation is added.
  */
 
-import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { describe, it, expect, vi, beforeEach, beforeAll } from 'vitest';
 
 // This import fails (RED) — broker/outboxWorker.ts does not exist yet.
 // eslint-disable-next-line @typescript-eslint/ban-ts-comment
 // @ts-ignore intentional RED import
-import { runOutboxDrain, assembleRruleString, scheduleOutboxDrain } from '../../src/broker/outboxWorker.js';
+import { runOutboxDrain, assembleRruleString, scheduleOutboxDrain, initOutboxTrigger } from '../../src/broker/outboxWorker.js';
 import { signalOutboxDrain } from '../../src/lib/outboxTrigger.js';
 
 // ── Drizzle DB mock ────────────────────────────────────────────────────────
@@ -745,6 +745,13 @@ describe('FREQ persistence (D-07 regression)', () => {
 // RED: these tests fail because scheduleOutboxDrain is not yet exported.
 
 describe('scheduleOutboxDrain — trigger wiring (D-09)', () => {
+  // Wire the EventEmitter signal → scheduleOutboxDrain once for this describe block.
+  // initOutboxTrigger registers the 'drain' listener that connects signalOutboxDrain()
+  // to scheduleOutboxDrain(). Called once (not per-test) to avoid listener accumulation.
+  beforeAll(() => {
+    initOutboxTrigger();
+  });
+
   beforeEach(() => {
     vi.resetAllMocks();
     mockPendingRows = [];
@@ -818,6 +825,8 @@ describe('scheduleOutboxDrain — trigger wiring (D-09)', () => {
 
   // Test C (SC-4 / D-07): two concurrent scheduleOutboxDrain() calls dispatch each row
   // exactly once — the second call is a no-op via the isDraining guard.
+  // The trailing re-drain (triggered by drainRequested) finds 0 pending rows so
+  // createCalendarEvent is called exactly once total.
   it('D-07: two concurrent scheduleOutboxDrain() calls invoke createCalendarEvent exactly once', async () => {
     vi.useFakeTimers();
     try {
@@ -829,14 +838,20 @@ describe('scheduleOutboxDrain — trigger wiring (D-09)', () => {
             setTimeout(() => resolve(makeResponse(201)), 20),
           ),
       );
-      mockPendingRows = [makeRow({ id: 1 })];
+      const row = makeRow({ id: 1 });
+      // First pending-rows query returns the row; subsequent queries return empty
+      // (simulates: drain 1 processes and removes the row; trailing drain finds nothing)
+      mockWherePending
+        .mockImplementationOnce(() => Promise.resolve([row]))
+        .mockImplementation(() => Promise.resolve([]));
 
-      // Both calls are synchronous — second must no-op via isDraining guard
+      // Both calls are synchronous — second sees isDraining=true and sets drainRequested=true
       scheduleOutboxDrain();
       scheduleOutboxDrain();
 
       await vi.runAllTimersAsync();
 
+      // Drain 1 dispatched the row once; trailing drain found 0 rows → createCalendarEvent once total
       expect(createCalendarEvent).toHaveBeenCalledTimes(1);
     } finally {
       vi.useRealTimers();