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/routing.service.ts

@@ -1,4 +1,4 @@
-import { Injectable, Logger } from '@nestjs/common';
+import { Inject, Injectable, Logger } from '@nestjs/common';
 import type { ModelInfo } from '@mosaic/types';
 import type { RoutingCriteria, RoutingResult, CostTier } from '@mosaic/types';
 import { ProviderService } from './provider.service.js';
@@ -14,7 +14,7 @@ const COST_TIER_THRESHOLDS: Record<CostTier, { maxInput: number }> = {
 export class RoutingService {
   private readonly logger = new Logger(RoutingService.name);
 
-  constructor(private readonly providerService: ProviderService) {}
+  constructor(@Inject(ProviderService) private readonly providerService: ProviderService) {}
 
   /**
    * Select the best available model for the given criteria.