feat: add DeepSeek and Xiaomi MiMo LLM provider presets

- Add providers.py with 5 provider presets (OpenAI, DeepSeek, Xiaomi MiMo, Alibaba DashScope, MiniMax)
- Add LLM_PROVIDER env var for one-line provider switching
- Improve <think> tag stripping for reasoning models
- Add .env.example with documented configuration
- Update README with provider configuration section

README.md

@@ -116,17 +116,48 @@ cp .env.example .env
 
 ```env
 # LLM API Configuration (supports any LLM API with OpenAI SDK format)
-# Recommended: Alibaba Qwen-plus model via Bailian Platform: https://bailian.console.aliyun.com/
-# High consumption, try simulations with fewer than 40 rounds first
+# Option 1 (Recommended): Use provider preset - just set provider name and API key
+LLM_PROVIDER=deepseek
 LLM_API_KEY=your_api_key
-LLM_BASE_URL=https://dashscope.aliyuncs.com/compatible-mode/v1
-LLM_MODEL_NAME=qwen-plus
+
+# Option 2: Manual configuration (compatible with original method)
+# LLM_BASE_URL=https://api.deepseek.com/v1
+# LLM_MODEL_NAME=deepseek-chat
 
 # Zep Cloud Configuration
 # Free monthly quota is sufficient for simple usage: https://app.getzep.com/
 ZEP_API_KEY=your_zep_api_key
 ```
 
+**Supported LLM Providers:**
+
+| Provider | `LLM_PROVIDER` | Default Model | Notes |
+|----------|-----------------|---------------|-------|
+| **DeepSeek** | `deepseek` | `deepseek-chat` | Cost-effective, reasoning model available (`deepseek-reasoner`) |
+| **Xiaomi MiMo** | `xiaomi_mimo` | `mimo-v2.5-pro` | Fast inference, competitive performance |
+| **OpenAI** | `openai` | `gpt-4o-mini` | Industry standard |
+| **Alibaba DashScope** | `alibaba_dashscope` | `qwen-plus` | High consumption, try <40 rounds first |
+| **MiniMax** | `minimax` | `MiniMax-M2.5` | Good for Chinese content |
+
+**Quick Examples:**
+
+```bash
+# DeepSeek (Recommended for cost-effectiveness)
+LLM_PROVIDER=deepseek
+LLM_API_KEY=sk-you...n
+
+# Xiaomi MiMo (Fast inference)
+LLM_PROVIDER=xiaomi_mimo
+LLM_API_KEY=your-m...n
+```
+
+> **Note**: You can override the default model by also setting `LLM_MODEL_NAME`:
+> ```env
+> LLM_PROVIDER=deepseek
+> LLM_API_KEY=sk-you...n
+> LLM_MODEL_NAME=deepseek-reasoner  # Use reasoning model
+> ```
+
 #### 2. Install Dependencies
 
 ```bash