fix(gateway): resolve InteractionCoordinationService handoff factory via optional DI token (#1145)

root cause: emitDecoratorMetadata reflected the third constructor parameter as Function and Nest attempted to resolve it

fix: optional HANDOFF_ID_FACTORY injection token, no production provider, preserving undefined -> crypto.randomUUID() default and unchanged positional construction

TDD: real CoordModule red at Function index [2], then green; test overrides only unrelated AuthGuard because its AUTH provider comes from AppModule's global AuthModule context

Closes #1145

apps/gateway/src/coord/interaction-coordination.di.test.ts

@@ -0,0 +1,19 @@
+import 'reflect-metadata';
+import { Test } from '@nestjs/testing';
+import { describe, expect, it } from 'vitest';
+import { CoordModule } from './coord.module.js';
+import { InteractionCoordinationService } from './interaction-coordination.service.js';
+import { AuthGuard } from '../auth/auth.guard.js';
+
+describe('CoordModule DI (compiled-metadata boot)', () => {
+  it('resolves InteractionCoordinationService through Nest DI', async () => {
+    const moduleRef = await Test.createTestingModule({ imports: [CoordModule] })
+      .overrideGuard(AuthGuard)
+      .useValue({ canActivate: (): boolean => true })
+      .compile();
+    expect(moduleRef.get(InteractionCoordinationService)).toBeInstanceOf(
+      InteractionCoordinationService,
+    );
+    await moduleRef.close();
+  });
+});