7h/day coding sandbox: Agent37, boxd, then boat

For one coding sandbox awake about 7 hours a day with files kept on resume: Agent37 default (gVisor, 4 vCPU/8 GB, 20 GB disk cap, US only) is about $4.30 because sleep bills disk at $0.09/GB-month. boxd.sh is a real KVM VM with SSH and Docker; their own calculator is about EUR 9/month for 2 vCPU/8 GB at 8h and 10% CPU, and a pegged machine is far more. boat.dev default is 4 vCPU/8 GB at $0.036/hour wall-clock (~$7.56) but the smallest plan is $20/month and unused hours do not roll over; stopped disks are kept at least 14 days. E2B and Daytona list $0.0504/vCPU-hour plus $0.0162/GiB-hour, about $70 for 210 hours of 4/8. boxes.dev charges $0.40 per 4/8 box-hour after the plan's included hours.