fix(provider): derive reasoning variants from models.dev

packages/core/test/plugin/fixtures/models-dev.json

@@ -10,5 +10,25 @@
     "name": "Local",
     "env": [],
     "models": {}
+  },
+  "opencode": {
+    "id": "opencode",
+    "name": "OpenCode",
+    "env": [],
+    "npm": "@ai-sdk/openai-compatible",
+    "models": {
+      "gpt-5.5": {
+        "id": "gpt-5.5",
+        "name": "GPT-5.5",
+        "release_date": "2026-04-23",
+        "attachment": true,
+        "reasoning": true,
+        "reasoning_options": [{ "type": "effort", "values": [null, "none", "low", "medium", "high", "xhigh"] }],
+        "temperature": false,
+        "tool_call": true,
+        "limit": { "context": 400000, "output": 128000 },
+        "provider": { "npm": "@ai-sdk/openai", "api": "https://console.opencode.ai/inference/openai/v1" }
+      }
+    }
   }
 }