fix: prevent runtime size deselection

[xingyaoww]

Description

Fixes an issue where users could deselect the runtime setting (1x) in the frontend settings, which should not be possible.

Changes

• Added selectionMode="single" to ensure only one option can be selected
• Added isRequired={true} to prevent deselection of the value

Testing

• Verified that runtime setting cannot be deselected
• All frontend tests pass
• Frontend builds successfully

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:b2cdcbf-nikolaik   --name openhands-app-b2cdcbf   docker.all-hands.dev/all-hands-ai/openhands:b2cdcbf

[mamoodi]

It sort of works? It still allows deselection but at least now it gives you a warning that something needs to be set.

[xingyaoww]

@mamoodi how about now

[mamoodi]

Something is off here. With this change, when I Save advanced settings, and then reopen settings, it goes back to the basic settings. Really weird.
Let's hold off on this because it's not critical.