Fixed types and created tests

lib/llm/grok.mjs

@@ -10,15 +10,15 @@ export class GrokProvider extends LLMProvider {
     this.model = config.model || 'grok-3';
   }
 
-  getConfigured() {
+  get isConfigured() {
     return !!this.apiKey;
   }
 
   async complete(systemPrompt, userMessage, opts = {}) {
     const res = await fetch('https://api.x.ai/v1/chat/completions', {
-      method: POST,
+      method: 'POST',
       headers: {
-        'Content-type': 'application/json',
+        'Content-Type': 'application/json',
         Authorization: `Bearer ${this.apiKey}`,
       },
       body: JSON.stringify({