[sahiljagtap08]

Closes #158

#158 asks whether Qwen and DeepSeek are supported. They already are (engine_type qwen and deepseek in LMMAgent), but neither is mentioned anywhere in the README, and the DeepSeek path is broken from the CLI.

Bug

LMMAgent fills in DeepSeek's default endpoint only when the base_url key is absent:

elif engine_type == "deepseek":
    if "base_url" not in engine_params:

cli_app.py always builds engine_params with "base_url": args.model_url, which is "" unless --model_url is given. So agent_s --provider deepseek --model deepseek-chat constructs LMMEngineOpenAI(base_url=""), and since that engine treats a falsy base_url as "use the default", the DeepSeek API key is sent to api.openai.com and the run fails with an OpenAI auth error. The qwen branch already checks not engine_params.get("base_url"); deepseek now does the same.

Reproduction on main:

os.environ["DEEPSEEK_API_KEY"] = "sk-x"
LMMAgent({"engine_type": "deepseek", "model": "deepseek-chat", "base_url": "", "api_key": ""}).engine.base_url
# ''   -> should be 'https://api.deepseek.com/v1'

Docs

• README gains a Supported Providers table under the CLI section: every accepted --provider value, the credential env var it reads, and how its endpoint is resolved (verified against engine.py / mllm.py). It includes a Qwen-on-DashScope example and notes that self-hosted Qwen-VL / DeepSeek behind vLLM, SGLang etc. work via --provider openai --model_url.
• --provider CLI help lists the accepted values instead of "openai, anthropic, etc.".

Tests

Added to tests/test_providers.py:

• CLI-shaped params (base_url="", api_key="") resolve DeepSeek's and Qwen's default endpoints and pick up the key from the environment. The DeepSeek case fails on main ('' != 'https://api.deepseek.com/v1') and passes with the fix.
• an explicit DeepSeek base_url is kept
• missing DEEPSEEK_API_KEY / QWEN_API_KEY raise the documented error
• an unknown provider raises

$ python -m pytest tests/test_providers.py -q
11 passed
$ black --check gui_agents/s3/core/mllm.py gui_agents/s3/cli_app.py tests/test_providers.py
3 files would be left unchanged.