feat(service): P3.2 InboxProjector + message.read event + scheduled relay

Event-driven projector creates/collapses NEEDS_REPLY items from message.sent
(traceId propagated; inbox.item.created emitted) and resolves them to DONE on
message.read; idempotent via processed-event ledger. markRead now emits a
message.read outbox event (atomic). OutboxRelay runs on a 500ms timer in the
app (off in tests). Shared resetDb (TRUNCATE CASCADE) fixes cross-spec FK
isolation. 32 tests green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-service/src/test-utils/reset-db.ts

@@ -0,0 +1,16 @@
+import type { PrismaClient } from '@prisma/client';
+
+/**
+ * FK-safe full reset for DB-backed specs. TRUNCATE … CASCADE clears every kernel
+ * table regardless of relation order, so specs don't each need to know the full
+ * delete order (which broke once Inbox added FK references to interaction/thread/actor).
+ */
+export async function resetDb(prisma: PrismaClient): Promise<void> {
+  await prisma.$executeRawUnsafe(
+    `TRUNCATE TABLE
+      "IiosInboxItemStateHistory","IiosInboxItem","IiosUnreadCounter","IiosMessageReceipt",
+      "IiosOutboxEvent","IiosProcessedEvent","IiosMessagePart","IiosInteraction",
+      "IiosThreadParticipant","IiosThread","IiosActorRef","IiosSourceHandle","IiosChannel","IiosScope"
+      RESTART IDENTITY CASCADE`,
+  );
+}