feat: foundation — Docker Compose, OTEL, shared types (P0-002, P0-005, P0-006)

Docker Compose (P0-005):
- PG 17 + pgvector, Valkey 8, OTEL Collector, Jaeger
- OTEL Collector config with trace/metric/log pipelines
- .env.example with all connection strings

OTEL Foundation (P0-006):
- @opentelemetry/sdk-node with auto-instrumentations
- tracing.ts loaded before NestJS bootstrap
- OTLP HTTP exporter → collector → Jaeger
- Disabled fs/dns instrumentations (noisy)

Shared Types (P0-002):
- ChatMessageDto with class-validator (IsUUID, IsNotEmpty, MaxLength)
- ChatResponseDto for REST responses
- Socket.IO typed event maps (ServerToClientEvents, ClientToServerEvents)
- AgentSessionHandle opaque type
- All event payload interfaces shared across gateway/cli/discord

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/gateway/package.json

@@ -12,12 +12,19 @@
     "test": "vitest run"
   },
   "dependencies": {
+    "@mariozechner/pi-coding-agent": "~0.57.1",
     "@nestjs/common": "^11.0.0",
     "@nestjs/core": "^11.0.0",
     "@nestjs/platform-fastify": "^11.0.0",
     "@nestjs/platform-socket.io": "^11.0.0",
     "@nestjs/websockets": "^11.0.0",
-    "@mariozechner/pi-coding-agent": "~0.57.1",
+    "@opentelemetry/auto-instrumentations-node": "^0.71.0",
+    "@opentelemetry/exporter-metrics-otlp-http": "^0.213.0",
+    "@opentelemetry/exporter-trace-otlp-http": "^0.213.0",
+    "@opentelemetry/resources": "^2.6.0",
+    "@opentelemetry/sdk-metrics": "^2.6.0",
+    "@opentelemetry/sdk-node": "^0.213.0",
+    "@opentelemetry/semantic-conventions": "^1.40.0",
     "fastify": "^5.0.0",
     "reflect-metadata": "^0.2.0",
     "rxjs": "^7.8.0",

apps/gateway/src/main.ts

@@ -1,16 +1,21 @@
+import './tracing.js';
 import 'reflect-metadata';
 import { NestFactory } from '@nestjs/core';
+import { Logger } from '@nestjs/common';
 import { FastifyAdapter, type NestFastifyApplication } from '@nestjs/platform-fastify';
 import { AppModule } from './app.module.js';
 
 async function bootstrap(): Promise<void> {
+  const logger = new Logger('Bootstrap');
   const app = await NestFactory.create<NestFastifyApplication>(AppModule, new FastifyAdapter());
 
-  await app.listen(4000, '0.0.0.0');
-  console.log('Gateway listening on port 4000');
+  const port = process.env['GATEWAY_PORT'] ?? 4000;
+  await app.listen(port as number, '0.0.0.0');
+  logger.log(`Gateway listening on port ${port}`);
 }
 
 bootstrap().catch((err: unknown) => {
-  console.error(err);
+  const logger = new Logger('Bootstrap');
+  logger.error('Fatal startup error', err instanceof Error ? err.stack : String(err));
   process.exit(1);
 });

apps/gateway/src/tracing.ts

@@ -0,0 +1,42 @@
+import { NodeSDK } from '@opentelemetry/sdk-node';
+import { getNodeAutoInstrumentations } from '@opentelemetry/auto-instrumentations-node';
+import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-http';
+import { OTLPMetricExporter } from '@opentelemetry/exporter-metrics-otlp-http';
+import { PeriodicExportingMetricReader } from '@opentelemetry/sdk-metrics';
+import { resourceFromAttributes } from '@opentelemetry/resources';
+import { ATTR_SERVICE_NAME, ATTR_SERVICE_VERSION } from '@opentelemetry/semantic-conventions';
+
+const otlpEndpoint = process.env['OTEL_EXPORTER_OTLP_ENDPOINT'] ?? 'http://localhost:4318';
+
+const sdk = new NodeSDK({
+  resource: resourceFromAttributes({
+    [ATTR_SERVICE_NAME]: process.env['OTEL_SERVICE_NAME'] ?? 'mosaic-gateway',
+    [ATTR_SERVICE_VERSION]: '0.0.0',
+  }),
+  traceExporter: new OTLPTraceExporter({
+    url: `${otlpEndpoint}/v1/traces`,
+  }),
+  metricReader: new PeriodicExportingMetricReader({
+    exporter: new OTLPMetricExporter({
+      url: `${otlpEndpoint}/v1/metrics`,
+    }),
+    exportIntervalMillis: 15_000,
+  }),
+  instrumentations: [
+    getNodeAutoInstrumentations({
+      '@opentelemetry/instrumentation-fs': { enabled: false },
+      '@opentelemetry/instrumentation-dns': { enabled: false },
+    }),
+  ],
+});
+
+sdk.start();
+
+process.on('SIGTERM', () => {
+  sdk
+    .shutdown()
+    .then(() => process.exit(0))
+    .catch(() => process.exit(1));
+});
+
+export { sdk };