Auto mode now backs off and stops the turn if the server-side safety check stays unavailable

What

• When Auto mode's server-side safety classifier repeatedly returns no usable verdict, Claude Code now waits with backoff and reports this as a new auto_mode_unavailable retry status.
• The UI shows a matching new state, 'Auto mode check unavailable', with a countdown ('next try in … attempt X/Y') and a hint that you can press escape to interrupt.
• After a fixed number of consecutive failures, Claude Code stops retrying, denies the tool call, and ends the turn instead of looping forever. This is tracked by the tengu_auto_mode_unavailable_stop event.

Why

Without this, a server-side classifier outage could leave Auto mode retrying indefinitely with no clear feedback. Now you see what's happening and the turn eventually gives up cleanly instead of hanging.