feat: add Cerebras provider support (#7339)

Signed-off-by: Max Novich <maxnovich@users.noreply.github.com>
Signed-off-by: Max Novich <maxnovich@Maxs-Mac-mini.local>
Co-authored-by: Max Novich <maxnovich@Maxs-Mac-mini.local>

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

@@ -0,0 +1,27 @@
+{
+  "name": "cerebras",
+  "engine": "openai",
+  "display_name": "Cerebras",
+  "description": "Fast inference on Cerebras wafer-scale engines",
+  "api_key_env": "CEREBRAS_API_KEY",
+  "base_url": "https://api.cerebras.ai/v1/chat/completions",
+  "models": [
+    {
+      "name": "llama3.1-8b",
+      "context_limit": 131072
+    },
+    {
+      "name": "gpt-oss-120b",
+      "context_limit": 131072
+    },
+    {
+      "name": "qwen-3-235b-a22b-instruct-2507",
+      "context_limit": 131072
+    },
+    {
+      "name": "zai-glm-4.7",
+      "context_limit": 131072
+    }
+  ],
+  "supports_streaming": true
+}