feat: add LLM config module for OpenRouter API settings

Reads API key and model from environment variables. LLM is disabled by
default and auto-enables when OPENROUTER_API_KEY is set.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/config/__tests__/llmConfig.test.ts

@@ -0,0 +1,45 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { getLlmConfig } from '../llmConfig.js';
+
+describe('llmConfig', () => {
+  const originalEnv = process.env;
+
+  beforeEach(() => {
+    process.env = { ...originalEnv };
+  });
+
+  afterEach(() => {
+    process.env = originalEnv;
+  });
+
+  it('returns default config values', () => {
+    const config = getLlmConfig();
+    expect(config.model).toBe('arcee-ai/trinity-large-preview:free');
+    expect(config.maxTokens).toBe(200);
+    expect(config.temperature).toBe(0.8);
+    expect(config.requestsPerMinute).toBe(10);
+    expect(config.timeoutMs).toBe(15000);
+    expect(config.enabled).toBe(false);
+  });
+
+  it('reads API key from environment', () => {
+    process.env.OPENROUTER_API_KEY = 'test-key-123';
+    const config = getLlmConfig();
+    expect(config.apiKey).toBe('test-key-123');
+    expect(config.enabled).toBe(true);
+  });
+
+  it('is disabled when no API key is set', () => {
+    delete process.env.OPENROUTER_API_KEY;
+    const config = getLlmConfig();
+    expect(config.apiKey).toBe('');
+    expect(config.enabled).toBe(false);
+  });
+
+  it('allows model override via environment', () => {
+    process.env.OPENROUTER_API_KEY = 'key';
+    process.env.LLM_MODEL = 'custom/model:free';
+    const config = getLlmConfig();
+    expect(config.model).toBe('custom/model:free');
+  });
+});

server/src/config/llmConfig.ts

@@ -0,0 +1,22 @@
+export interface LlmConfig {
+  apiKey: string;
+  model: string;
+  maxTokens: number;
+  temperature: number;
+  requestsPerMinute: number;
+  timeoutMs: number;
+  enabled: boolean;
+}
+
+export function getLlmConfig(): LlmConfig {
+  const apiKey = process.env.OPENROUTER_API_KEY ?? '';
+  return {
+    apiKey,
+    model: process.env.LLM_MODEL ?? 'arcee-ai/trinity-large-preview:free',
+    maxTokens: 200,
+    temperature: 0.8,
+    requestsPerMinute: 10,
+    timeoutMs: 15000,
+    enabled: apiKey.length > 0,
+  };
+}