Vietnamese Pork-and-Noodle Soup

1 1/2 tablespoons cooking oil

1 pork tenderloin (about 3/4 pound), cut into 1 1/2-by- 1/2-by- 1/2-inch strips

6 scallion s including green tops, chopped

1 tablespoon chopped fresh ginger

2 tomato es, chopped

3 tablespoons Asian fish sauce (nam pla or nuoc mam)

1 teaspoon salt

2 cups water

1 quart canned low-sodium chicken broth or homemade stock

1/4 pound bean sprouts

2 tablespoons lime juice (from about 1 lime), plus lime wedges for serving

1 cucumber , peeled, halved lengthwise, seeded, and cut crosswise into thin slices

1 cup lightly packed mint , basil, or cilantro leaves, or a combination