Route jobs through RelayRunner

Routing a job is one change: a relay job in front of it, and a runs-on that points at the relay's answer. The relay asks RelayRunner where the job should run and finishes in about a second without a runner. The job's old label stays as the fallback.

relayrunner init makes that change. It decides which jobs are safe to route and writes the YAML, keeping comments and formatting. Use it instead of writing relay YAML from memory, and only hand-edit a job init skipped when the user asks.

Work in the user's checkout and ask before changing files. init never commits; leave committing and pushing to the user unless they ask. If the CLI isn't installed, see the relayrunner skill.

1. Plan

relayrunner init --plan --json

This changes nothing. It returns the repo, its visibility, the relay version, and one entry per job: