docs: add llama.cpp local model configuration (#2931) - #5688

Summary

• document how to connect DeerFlow to a local llama.cpp llama-server
• add OpenAI-compatible Qwen examples to config.example.yaml and the English/Chinese configuration pages
• document Docker networking and tool-calling/chat-template requirements

Why

Issue #2931 asks how to configure a Qwen model served locally by llama.cpp in config.yaml.

DeerFlow already supports OpenAI-compatible endpoints through langchain_openai:ChatOpenAI, but current main does not include a llama.cpp configuration example. A previous attempt in #2960 was closed without being merged, and the documentation gap remains.

What changed

The examples use llama.cpp's OpenAI-compatible /v1/chat/completions endpoint:

models:
  - name: qwen-llamacpp
    use: langchain_openai:ChatOpenAI
    model: qwen-local
    api_key: no-key
    base_url: http://localhost:8080/v1
    request_timeout: 600.0
    max_retries: 2
    supports_vision: false

The docs also explain:

• using --alias qwen-local for a stable API model name
• using a container-reachable host instead of localhost when DeerFlow runs in Docker
• replacing the placeholder API key when llama-server --api-key is enabled
• ensuring the model chat template supports function/tool calls; current llama.cpp enables its Jinja chat-template engine by default

Validation

• verified the branch is based on the current upstream main
• verified the diff is limited to three documentation/configuration files
• verified current main contains no llama.cpp configuration example
• checked DeerFlow's current ModelConfig / model factory behavior for ChatOpenAI and base_url
• checked current llama.cpp server documentation for OpenAI-compatible chat completions, model aliases, Jinja chat templates, and function/tool calling
• repository CI will provide the authoritative formatting/build/test result for this PR

Closes #2931