fix(model-selector): prevent saving empty default model

- throw a toast error when user is trying to click on `set as default` without actually choosing the model(s).
- feat: added hmr for local development. use `npm run dev` and you get the hmr when debugging.

vite.config.ts

@@ -2,5 +2,8 @@ import { sveltekit } from '@sveltejs/kit/vite';
 import { defineConfig } from 'vite';
 
 export default defineConfig({
-	plugins: [sveltekit()]
+	plugins: [sveltekit()],
+	server: {
+		hmr: true
+	}
 });