feat: add Avian as a model provider (#4448)

Author: avianion

website/docs/references/models-http-api/avian.md

@@ -0,0 +1,50 @@
+# Avian
+
+[Avian](https://avian.io/) is an inference API provider offering access to frontier open-source models through an OpenAI-compatible endpoint. Available models include DeepSeek V3.2, Kimi K2.5, GLM-5, and MiniMax M2.5.
+
+## Chat Model
+
+Avian provides an OpenAI-compatible chat API interface.
+
+```toml title="~/.tabby/config.toml"
+[model.chat.http]
+kind = "openai/chat"
+model_name = "deepseek/deepseek-v3.2"
+api_endpoint = "https://api.avian.io/v1"
+api_key = "your-api-key"
+```
+
+You can also configure multi-model support to switch between available models:
+
+```toml title="~/.tabby/config.toml"
+[model.chat.http]
+kind = "openai/chat"
+model_name = "deepseek/deepseek-v3.2"
+supported_models = [
+  "deepseek/deepseek-v3.2",
+  "moonshotai/kimi-k2.5",
+  "z-ai/glm-5",
+  "minimax/minimax-m2.5"
+]
+api_endpoint = "https://api.avian.io/v1"
+api_key = "your-api-key"
+```
+
+## Completion Model
+
+Avian does not currently offer a dedicated completion (FIM) API endpoint.
+
+## Embeddings Model
+
+Avian does not currently offer embedding model APIs.
+
+## Available Models
+
+| Model | Context Length | Max Output |
+|---|---|---|
+| `deepseek/deepseek-v3.2` | 164K | 65K |
+| `moonshotai/kimi-k2.5` | 131K | 8K |
+| `z-ai/glm-5` | 131K | 16K |
+| `minimax/minimax-m2.5` | 1M | 1M |
+
+For the latest model list and pricing, visit [Avian](https://avian.io/).