fix(opencode): reject save when no models configured (#932)

Add validation to require at least one model before saving an OpenCode
provider. Shows a localized toast error when models are empty.

src/components/providers/forms/ProviderForm.tsx

@@ -746,7 +746,7 @@ export function ProviderForm({
       return;
     }
 
-    // OpenCode: validate provider key
+    // OpenCode: validate provider key and models
     if (appId === "opencode") {
       const keyPattern = /^[a-z0-9]+(-[a-z0-9]+)*$/;
       if (!opencodeProviderKey.trim()) {
@@ -761,6 +761,11 @@ export function ProviderForm({
         toast.error(t("opencode.providerKeyDuplicate"));
         return;
       }
+      // Validate that at least one model is configured
+      if (Object.keys(opencodeModels).length === 0) {
+        toast.error(t("opencode.modelsRequired"));
+        return;
+      }
     }
 
     // 非官方供应商必填校验：端点和 API Key