fix: add missing @Inject() decorators and fix coord workspace root detection

- Add @Inject() to all gateway constructor params (required without emitDecoratorMetadata)
  - AgentService: ProviderService, CoordService
  - RoutingService: ProviderService
  - ProvidersController: ProviderService, RoutingService
  - SessionsController: AgentService
- Fix coord controller ALLOWED_ROOTS to walk up to monorepo root (pnpm-workspace.yaml)
- Gateway now boots and serves all routes correctly

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

apps/gateway/src/agent/providers.controller.ts

@@ -1,4 +1,4 @@
-import { Body, Controller, Get, Post, UseGuards } from '@nestjs/common';
+import { Body, Controller, Get, Inject, Post, UseGuards } from '@nestjs/common';
 import type { RoutingCriteria } from '@mosaic/types';
 import { AuthGuard } from '../auth/auth.guard.js';
 import { ProviderService } from './provider.service.js';
@@ -8,8 +8,8 @@ import { RoutingService } from './routing.service.js';
 @UseGuards(AuthGuard)
 export class ProvidersController {
   constructor(
-    private readonly providerService: ProviderService,
-    private readonly routingService: RoutingService,
+    @Inject(ProviderService) private readonly providerService: ProviderService,
+    @Inject(RoutingService) private readonly routingService: RoutingService,
   ) {}
 
   @Get()