Fix cypress importFeatures command broken by dialog restructuring

The last commit merged two DialogContent sections into one, which broke
two selectors in the importFeatures command:
- The Select dropdown click now uses [role="button"] instead of finding
  an input and clicking its parent (which matched 3 inputs after the merge)
- The delete-features checkbox now uses cy.contains('label', ...) to
  unambiguously scope to the FormControlLabel element, and updates the
  label text from "Yes, delete existing features" to "Delete existing
  features" to match the new UI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: garrettjstevens

packages/jbrowse-plugin-apollo/cypress/support/commands.ts

@@ -280,25 +280,19 @@ Cypress.Commands.add(
             cy.get('input[type="file"]').selectFile(gffFile)
           })
 
-        cy.contains('Select assembly')
-          .parent()
-          .within(() => {
-            cy.get('input').parent().click()
-          })
+        cy.get('[role="button"]').click()
       })
     cy.contains('li', assemblyName, { timeout: 10_000 }).click()
 
     if (deleteExistingFeatures !== undefined) {
-      cy.contains('Yes, delete existing features')
-        .parent()
-        .within(() => {
-          if (deleteExistingFeatures) {
-            cy.get('input[type="checkbox"]').click()
-            cy.get('input[type="checkbox"]').should('be.checked')
-          } else {
-            cy.get('input[type="checkbox"]').should('be.not.checked')
-          }
-        })
+      cy.contains('label', 'Delete existing features').within(() => {
+        if (deleteExistingFeatures) {
+          cy.get('input[type="checkbox"]').click()
+          cy.get('input[type="checkbox"]').should('be.checked')
+        } else {
+          cy.get('input[type="checkbox"]').should('be.not.checked')
+        }
+      })
     }
 
     cy.contains('button', 'Submit').click()