fix(agent): register Ollama directly with api: openai-completions

Pi SDK requires an api field on provider/model registration. Ollama
uses the OpenAI-compatible completions API. Register directly via
registry.registerProvider instead of the generic wrapper to pass the
correct api type.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -92,15 +92,16 @@ export class ProviderService implements OnModuleInit {
       .map((modelId: string) => modelId.trim())
       .filter(Boolean);
 
-    this.registerCustomProvider({
-      id: 'ollama',
-      name: 'Ollama',
+    this.registry.registerProvider('ollama', {
       baseUrl: `${ollamaUrl}/v1`,
       apiKey: 'ollama',
+      api: 'openai-completions' as never,
       models: modelIds.map((id) => ({
         id,
         name: id,
         reasoning: false,
+        input: ['text'] as ('text' | 'image')[],
+        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
         contextWindow: 8192,
         maxTokens: 4096,
       })),