Udon Noodle Stir Fry

Name: Udon Noodle Stir Fry
Ingredients: 12 oz Udon noodles (fresh or frozen); 1 tablespoon vegetable oil (or sesame oil for extra flavor); 1 cup sliced bell peppers (any color); 1 cup sliced carrots; 1/2 cup sliced onions; 1/2 cup snap peas or snow peas; 2 cloves garlic (minced); 1 tablespoon ginger (minced); 3 tablespoons soy sauce (or tamari for gluten-free); 1 tablespoon oyster sauce (or vegetarian oyster sauce); 1 tablespoon sesame oil; 1 tablespoon rice vinegar; 1 teaspoon sugar (optional, for sweetness); 1 teaspoon chili paste or sriracha (optional, for heat); 1 cup cooked chicken shrimp, or tofu ( (optional but recommended for a full meal))