feat(M6): Set up orchestrator service foundation

Add NestJS-based orchestrator service structure for M6-AgentOrchestration.

Changes:
- Migrate from Express to NestJS architecture
- Add health check endpoint module
- Add placeholder modules: coordinator, git, killswitch, monitor, queue, spawner, valkey
- Update configuration for NestJS
- Update lockfile for new dependencies

This is foundational work for M6-AgentOrchestration milestone.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/orchestrator/src/main.ts

@@ -1,28 +1,19 @@
-/**
- * Mosaic Orchestrator - Agent Orchestration Service
- *
- * Execution plane for Mosaic Stack agent coordination.
- * Spawns, monitors, and manages Claude agents for autonomous work.
- */
+import { NestFactory } from "@nestjs/core";
+import { AppModule } from "./app.module";
+import { Logger } from "@nestjs/common";
 
-import { createServer } from './api/server.js';
-
-const PORT = process.env.ORCHESTRATOR_PORT || 3001;
+const logger = new Logger("Orchestrator");
 
 async function bootstrap() {
-  console.log('🚀 Starting Mosaic Orchestrator...');
-
-  const server = await createServer();
-
-  await server.listen({
-    port: Number(PORT),
-    host: '0.0.0.0'
+  const app = await NestFactory.create(AppModule, {
+    logger: ["error", "warn", "log", "debug", "verbose"],
   });
 
-  console.log(`✅ Orchestrator running on http://0.0.0.0:${PORT}`);
+  const port = process.env.ORCHESTRATOR_PORT ?? 3001;
+
+  await app.listen(Number(port), "0.0.0.0");
+
+  logger.log(`🚀 Orchestrator running on http://0.0.0.0:${String(port)}`);
 }
 
-bootstrap().catch((error) => {
-  console.error('Failed to start orchestrator:', error);
-  process.exit(1);
-});
+void bootstrap();