Add selected_repo to command line

[enyst]

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End-user friendly description of the problem this fixes or functionality that this introduces.

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Give a summary of what the PR does, explaining any non-trivial design decisions.

This PR proposes to add the ability to have a selected_repo in main.py. I would love something like this for debugging microagents rather than loading the UI all the time. Half the time will do. 😅

It's in sandbox_config, which is not read by evals, so it's a no-op for evals if we set it and forget it. (never happens!)

• selected_repo works in main.py
• selected_repo works in cli.py
• evals need a little tweak because connect is called here when the runtime is created.

Split from 6909

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Link of any specific issues this addresses.

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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:de193da-nikolaik   --name openhands-app-de193da   docker.all-hands.dev/all-hands-ai/openhands:de193da