test(05-01): add Wave-0 RED scaffolds + VAPID fixture + setup truncation

- tests/fixtures/vapid.ts: static TEST_VAPID keypair for offline unit tests
- tests/lib/pushDispatcher.test.ts: RED — 410/404 prune + 201/5xx no-delete
- tests/lib/pushCoalescer.test.ts: RED — burst coalesce fires once with count=N; excludeUserId
- tests/broker/reminderScheduler.test.ts: RED — shared+timed filter; dedup by (uid,minuteBucket)
- tests/lib/eventChangeDispatcher.test.ts: RED — create/meaningful-update fires; description-only silent; actor excluded
- tests/routes/push.test.ts: RED — POST 201/401; DELETE removes rows; GET vapid-public-key
- test/setup.ts: import pushSubscriptions + add db.delete(pushSubscriptions) in afterEach
- all 5 RED files fail on missing-module (correct; implementations in Plans 05-02..05-06)

apps/api/tests/lib/pushCoalescer.test.ts

@@ -0,0 +1,75 @@
+/**
+ * RED scaffold — pushCoalescer (Plan 05-03 turns this GREEN).
+ *
+ * Asserts that coalesceListPush:
+ *   - Fires the dispatch function exactly ONCE when N calls arrive within the coalesce window
+ *   - Passes the correct count (N) to the dispatch function
+ *   - Passes the actor's own userId as excludeUserId to suppress self-notifications (D-03)
+ *
+ * These tests fail now because pushCoalescer.ts does not yet exist.
+ * Run: pnpm --filter @familysync/api exec vitest run tests/lib/pushCoalescer.test.ts
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+
+describe('pushCoalescer — list-change burst coalescing (D-01)', () => {
+  beforeEach(() => {
+    vi.useFakeTimers()
+    vi.resetModules()
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('collapses N rapid coalesceListPush calls into a single dispatch with count=N', async () => {
+    const dispatch = vi.fn().mockResolvedValue(undefined)
+    const { coalesceListPush } = await import('../../src/lib/pushCoalescer.js')
+
+    const listId = 1
+    const actorId = 10
+    const N = 5
+
+    for (let i = 0; i < N; i++) {
+      coalesceListPush(listId, actorId, dispatch)
+    }
+
+    // Advance time past the coalesce window
+    await vi.runAllTimersAsync()
+
+    expect(dispatch).toHaveBeenCalledTimes(1)
+    const [calledListId, calledActorId, calledCount] = dispatch.mock.calls[0]
+    expect(calledListId).toBe(listId)
+    expect(calledCount).toBe(N)
+  })
+
+  it('passes the actor userId as excludeUserId so the actor does not notify themselves (D-03)', async () => {
+    const dispatch = vi.fn().mockResolvedValue(undefined)
+    const { coalesceListPush } = await import('../../src/lib/pushCoalescer.js')
+
+    const listId = 2
+    const actorId = 99
+
+    coalesceListPush(listId, actorId, dispatch)
+    await vi.runAllTimersAsync()
+
+    expect(dispatch).toHaveBeenCalledTimes(1)
+    const [, calledActorId] = dispatch.mock.calls[0]
+    expect(calledActorId).toBe(actorId)
+  })
+
+  it('fires separate dispatches for different lists independently', async () => {
+    const dispatch = vi.fn().mockResolvedValue(undefined)
+    const { coalesceListPush } = await import('../../src/lib/pushCoalescer.js')
+
+    coalesceListPush(1, 10, dispatch)
+    coalesceListPush(1, 10, dispatch)
+    coalesceListPush(2, 10, dispatch) // different list
+    coalesceListPush(2, 10, dispatch)
+
+    await vi.runAllTimersAsync()
+
+    // Two separate dispatches — one per distinct listId
+    expect(dispatch).toHaveBeenCalledTimes(2)
+  })
+})