doctor() fails on the renamed tailnet field of drukbox #78 #11

What happens

SandboxAPI.doctor() raises KeyError: 'tailscale_enabled' against a drukbox at or after "Join the tailnet per provider" (czpython/drukbox#78). That change renamed the field in the /doctor payload to tailnet:

{"ok": true, "active_provider": "docker-sbx", "tailnet": false, "checks": [...]}

DoctorReport still reads data["tailscale_enabled"]. Druks calls doctor() from druks doctor, so every deploy of druks against a current drukbox ends with "drukbox unreachable: 'tailscale_enabled'" although drukbox reports ok.

Expected

DoctorReport.tailnet reads tailnet, and tailscale_enabled from a drukbox before #78, so one SDK serves both. A release follows, so druks can move its pin.