Refine Ollama response content-type validation

Allow application/json and missing content-type headers, only rejecting
obvious non-JSON responses like HTML error pages. This improves
compatibility with different Ollama server configurations.

src/ollama-client.ts

@@ -163,8 +163,10 @@ export class OllamaClient {
       }
 
       const contentType = response.headers?.get?.('content-type');
-      if (contentType && !contentType.includes('application/x-ndjson')) {
-        throw new Error('Invalid response format');
+      // Ollama may return application/x-ndjson, application/json, or no content-type at all.
+      // Reject only obvious non-JSON responses (e.g., HTML error pages).
+      if (contentType && contentType.includes('text/html')) {
+        throw new Error('Invalid response format: server returned HTML instead of JSON');
       }
 
       reader = response.body.getReader();