feat: add Together AI declarative provider (#9545)

Signed-off-by: Varun Nuthalapati <nuthalapativarun@gmail.com>
Signed-off-by: Douwe M Osinga <douwe@sidewalklabs.com>
Co-authored-by: Douwe M Osinga <douwe@sidewalklabs.com>

crates/goose/src/providers/declarative/together.json

@@ -0,0 +1,49 @@
+{
+  "name": "together",
+  "engine": "openai",
+  "display_name": "Together AI",
+  "description": "Open-source and custom AI models via Together AI's OpenAI-compatible API.",
+  "api_key_env": "TOGETHER_API_KEY",
+  "base_url": "https://api.together.xyz/v1",
+  "catalog_provider_id": "togetherai",
+  "dynamic_models": true,
+  "models": [
+    {
+      "name": "meta-llama/Llama-3.3-70B-Instruct-Turbo",
+      "context_limit": 131072
+    },
+    {
+      "name": "deepseek-ai/DeepSeek-V3",
+      "context_limit": 131072
+    },
+    {
+      "name": "deepseek-ai/DeepSeek-R1",
+      "context_limit": 163839
+    },
+    {
+      "name": "Qwen/Qwen3-Coder-480B-A35B-Instruct-FP8",
+      "context_limit": 262144
+    },
+    {
+      "name": "Qwen/Qwen3-235B-A22B-Instruct-2507-tput",
+      "context_limit": 262144
+    },
+    {
+      "name": "moonshotai/Kimi-K2.5",
+      "context_limit": 262144
+    },
+    {
+      "name": "openai/gpt-oss-120b",
+      "context_limit": 131072
+    }
+  ],
+  "preserves_thinking": true,
+  "supports_streaming": true,
+  "model_doc_link": "https://docs.together.ai/docs/inference-models",
+  "setup_steps": [
+    "Sign in to https://api.together.xyz",
+    "Navigate to API Keys in your account settings",
+    "Create a new API key",
+    "Copy the key and paste it above"
+  ]
+}