1/2 pound haricots verts or other green beans, cut into 3/4-inch lengths
1 tablespoon Dijon mustard
1 teaspoon finely chopped shallot
2 tablespoons red-wine vinegar
1 tablespoon extra-virgin olive oil
8 hard-boiled large eggs, chopped
1/2 cup mayonnaise
2 celery ribs, finely chopped (1 cup)
2 tablespoons chopped chives
1 teaspoon grated lemon zest
1 teaspoon fresh lemon juice
4 cups coarsely chopped baby arugula
1/2 pound sliced smoked salmon, coarsely chopped
bagel chips