feat: detect OpenAI-compatible providers (MiniMax, Groq, etc.) in telemetry spans

[octo-patch]

Summary

When users use the OpenAI SDK with a custom base_url pointing to an OpenAI-compatible provider (e.g., MiniMax, Groq, DeepSeek), the gen_ai.system span attribute was always hardcoded to "OpenAI". This made it impossible to distinguish calls to different providers in observability dashboards.

This PR adds automatic provider detection by inspecting the OpenAI client base_url at instrumentation time:

• New file: provider_detection.py maps known API base URLs to provider names
• Modified: stream_wrapper.py chat completions and Responses API wrappers (sync + async) now detect the actual provider and set gen_ai.system accordingly
• 35 new tests covering all detection paths

Supported providers

Provider	Base URL pattern
MiniMax	api.minimax.io, api.minimax.chat
Groq	api.groq.com
Together AI	api.together.xyz, api.together.ai
Fireworks AI	api.fireworks.ai
DeepSeek	api.deepseek.com
Mistral AI	api.mistral.ai
Perplexity AI	api.perplexity.ai
Google AI	generativelanguage.googleapis.com
xAI	api.x.ai
SambaNova	api.sambanova.ai
Cerebras	api.cerebras.ai

Example

from openai import OpenAI
import agentops

agentops.init()

# This call will now have gen_ai.system="MiniMax" instead of "OpenAI"
client = OpenAI(
    api_key="your-minimax-key",
    base_url="https://api.minimax.io/v1"
)
response = client.chat.completions.create(
    model="MiniMax-M2.7",
    messages=[{"role": "user", "content": "Hello!"}]
)

Design decisions

• Detection only applies to chat completions and Responses API (wrapped via _custom_wrap), which are the primary LLM endpoints.
• Unknown base URLs default to "OpenAI" no behavior change for standard OpenAI usage.
• The provider host map is easily extensible.

Test plan

• 16 unit tests for _match_provider() covering all providers + edge cases
• 5 unit tests for _extract_base_url() covering string URLs, URL objects, missing attributes
• 8 unit tests for detect_provider_from_instance() end-to-end
• 6 integration tests simulating the full wrapper flow
• All 148 existing instrumentation tests still pass