Teleport handoff records more detail about why a handoff did not go through

When Claude Code hands a session over through teleport, it checks for a marker that tells it to pass the turn along. That check now records a specific reason when it does not go ahead, such as the relay not being set up or the turn already having been answered. Before, the reasons were free text.

It also records which stage it reached, records a warning if the marker is never used, and reports a failure during startup as boot_failed.