Self-hosted runner sessions now check the config directory's health before starting, flagging stuck NFS/CSI mounts
When a self-hosted runner starts a new session, it now runs an explicit check to see if the session's config directory is reachable, logging [runner:stuck] session config dir check ... (check NFS/CSI mount health) if something's wrong. This check happens before the runner sets up the rest of the session's internal state. If the check hits an unrecoverable error, a new failure flag is set that causes later cleanup steps to be skipped.
This helps diagnose sessions that hang because of a broken or slow network filesystem mount (NFS or CSI), pointing operators at the mount as the likely cause instead of leaving the session silently stuck.