Allow for devs to customize the default Agent Mode keybinding

As devs start to leverage custom agents more, both the dropdown will be getting larger, and the primary default will not alway be at the top, meaning that they will need to search for their dropdown to find the agent that they use every time, which can be a pain if it is in the middle of the list.

We currently support a Agent as being the defacto default but many devs actually use Ask as their default, or slight updates to agent, for example a dev that works at a finanancial institution that wants an Agent like experinence but wants to make sure that access to the web is shut off may create a slighly tweaked mode.

Having a Key Binding that sticks to customizable Default rather than just Agent would help.

Current State	Suggested State