Simulator GUI: Scenario toggles do opposite to what user expects

As a user of the simulator GUI I would like to filter the scenarios based on the scenario type (Starter, Non-starter) so that I can group the scenarios by type.

Background: the filters for the scenario page do the opposite to what the user expects. When "Starter" is selected then "Non-Starter" scenarios are displayed.

Start by reproducing the Starter and Non-Starter selections in the simulator GUI's scenario page, then trace the filter handling for those toggles. Done means selecting Starter displays Starter scenarios and selecting Non-Starter displays Non-Starter scenarios, with grouping behavior matching the selected type.

Written by the indexing model from the issue text.