Add hidden `entire auth token` for scripting

Prints the active control-plane bearer to stdout so curl/scripts can auth without digging the JWT out of the keychain:

curl -H "Authorization: Bearer $(entire auth token)" "$CORE/api/v1/clusters"

Honors ENTIRE_TOKEN verbatim, else resolves and refreshes the active context's login JWT (same bearer the API client uses). Hidden; errors and the not-logged-in hint go to stderr so stdout stays clean for command substitution.