Add UncommonRoute provider for intelligent LLM cost routing

[Vivien202]

Summary

Adds UncommonrouteProvider — a provider adapter for UncommonRoute, an intelligent LLM cost router.

What it does for aisuite users

UncommonRoute runs as a local proxy that analyzes each request and routes it to the cheapest model capable of handling it. Users get cost savings without changing their code — just swap the provider prefix:

# Before: always uses GPT-4
response = client.chat.completions.create(model="openai:gpt-4o", ...)

# After: routes to cheapest capable model
response = client.chat.completions.create(model="uncommonroute:auto", ...)

Three routing modes: auto (balanced), fast (cheapest), best (strongest).

Implementation

• Follows the existing HTTP-based provider pattern (similar to OllamaProvider)
• Uses httpx (already a project dependency) — no new dependencies
• Includes unit tests mirroring the existing provider test structure

Files

• aisuite/providers/uncommonroute_provider.py — provider implementation (81 lines)
• tests/providers/test_uncommonroute_provider.py — unit tests (67 lines)