Summary

• Add Avian as a new OpenAI-compatible LLM provider (https://api.avian.io/v1)
• New provider module (web/src/llm-api/avian.ts) following the same pattern as Fireworks/SiliconFlow, with streaming + non-streaming support, per-model pricing, usage/billing tracking, TTFT measurement, and error handling
• Route avian/* model IDs through the Avian provider in the chat completions API
• Add AVIAN_API_KEY to server env schema (optional, like other third-party provider keys)
• Register Avian models in model-config.ts constants, providerModelNames, providerDomains, and all three copies of the ModelName type

Models available via Avian

Test plan

• Verify isAvianModel() correctly matches only avian/* model IDs
• Test streaming and non-streaming requests route to Avian when model starts with avian/
• Confirm billing/credit consumption works correctly with Avian pricing
• Verify AvianError is caught and returned with proper status codes
• Check that non-Avian models still route to their existing providers (no regression)