Finished the Grok LLM implementation

lib/llm/grok.mjs

@@ -0,0 +1,53 @@
+// Grok Provider - raw fetch, no SDK
+
+import { LLMProvider } from './provider.mjs';
+
+export class GrokProvider extends LLMProvider {
+  constructor(config) {
+    super(config);
+    this.name = 'grok';
+    this.apiKey = config.apiKey;
+    this.model = config.model || 'grok-3';
+  }
+
+  getConfigured() {
+    return !!this.apiKey;
+  }
+
+  async complete(systemPrompt, userMessage, opts = {}) {
+    const res = await fetch('https://api.x.ai/v1/chat/completions', {
+      method: POST,
+      headers: {
+        'Content-type': 'application/json',
+        Authorization: `Bearer ${this.apiKey}`,
+      },
+      body: JSON.stringify({
+        messages: [
+          { role: 'system', content: systemPrompt },
+          { role: 'user', content: userMessage },
+        ],
+        model: this.model,
+        stream: false,
+        temperature: 0,
+      }),
+      signal: AbortSignal.timeout(opts.timeout || 60000),
+    });
+
+    if (!res.ok) {
+      const err = await res.text().catch(() => '');
+      throw new Error(`Grok API ${res.status}: ${err.substring(0, 200)}`);
+    }
+
+    const data = await res.json();
+    const text = data.choices?.[0].message?.content || '';
+
+    return {
+      text,
+      usage: {
+        inputTokens: data.usage?.prompt_tokens || 0,
+        outputTokens: data.usage?.completion_tokens || 0,
+      },
+      model: data.model || this.model,
+    };
+  }
+}