fix: config improvements

src/config/index.ts

@@ -24,9 +24,15 @@ export async function initConfig(old: AppConfig | null): Promise<AppConfig> {
   const models = await getModels(baseURL);
   const model = await autocomplete({
     message: "Choose a default model:",
-    initialValue: old?.model,
-    placeholder: old?.model,
+    initialValue: old?.model ?? models[0]?.value,
+    placeholder: old?.model ?? models[0]?.value,
     options: models,
+    validate: (value) =>
+      models
+        .map((model) => model.value)
+        .includes(typeof value === "string" ? value : "")
+        ? undefined
+        : `Unable to find model "${value}"`,
   });
   if (isCancel(model)) process.exit(1);