feat(llm): add NVIDIA NIM, Kimi, Groq, and Mistral providers

Each is a one-row entry in the OpenAI-compatible provider registry (base_url,
key env, CLI option); the model is user-specified since they serve many models.

cli/utils.py

@@ -311,6 +311,10 @@ def _llm_provider_table() -> list[tuple[str, str, str | None]]:
         ("GLM", "glm", "https://open.bigmodel.cn/api/paas/v4/"),
         ("MiniMax", "minimax", "https://api.minimax.io/v1"),
         ("OpenRouter", "openrouter", "https://openrouter.ai/api/v1"),
+        ("Mistral", "mistral", "https://api.mistral.ai/v1"),
+        ("Kimi (Moonshot)", "kimi", "https://api.moonshot.ai/v1"),
+        ("Groq", "groq", "https://api.groq.com/openai/v1"),
+        ("NVIDIA NIM", "nvidia", "https://integrate.api.nvidia.com/v1"),
         ("Azure OpenAI", "azure", None),
         ("Ollama", "ollama", ollama_url),
         ("OpenAI-compatible (vLLM, LM Studio, llama.cpp, custom relay)", "openai_compatible", None),