Self-hosted runners can renew their token and prepare a fresh machine per session

A self-hosted runner is a machine you run yourself that picks up Claude Code sessions to work on. Two things change:

• The runner can now renew its runner token, the credential it uses to receive work, instead of only fetching it once.
• Starting a session gains a freshMachinePerSession option. When it is set and the runner handles one session at a time, Claude Code starts the session with a different set of arguments.

The runner also drops its warmup report options. A new way to declare fresh-machine support through --runner-declares= is present but cannot take effect in this build, and the existing nested-repository declaration works as before.