feat(M3-003): OpenAI provider adapter for Codex gpt-5.4 (#310)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/agent/provider.service.ts

@@ -8,7 +8,7 @@ import type {
   ProviderHealth,
   ProviderInfo,
 } from '@mosaic/types';
-import { AnthropicAdapter, OllamaAdapter } from './adapters/index.js';
+import { AnthropicAdapter, OllamaAdapter, OpenAIAdapter } from './adapters/index.js';
 import type { TestConnectionResultDto } from './provider.dto.js';
 
 /** Default health check interval in seconds */
@@ -42,7 +42,11 @@ export class ProviderService implements OnModuleInit, OnModuleDestroy {
     this.registry = new ModelRegistry(authStorage);
 
     // Build the default set of adapters that rely on the registry
-    this.adapters = [new OllamaAdapter(this.registry), new AnthropicAdapter(this.registry)];
+    this.adapters = [
+      new OllamaAdapter(this.registry),
+      new AnthropicAdapter(this.registry),
+      new OpenAIAdapter(this.registry),
+    ];
 
     // Run all adapter registrations first (Ollama, Anthropic, and any future adapters)
     await this.registerAll();