Free-form string→string map. Server-enforced limits: up to 256 keys,
key length 1–256 bytes, value length ≤4096 bytes, total JSON encoding
≤65536 bytes.
envVarsEnvVars
Environment variable string→string map injected into the VM at boot.
Keys must be 1–256 bytes and match shell-variable name
([A-Za-z_][A-Za-z0-9_]*); values may not contain newline,
carriage return, or null bytes. Total JSON encoding ≤65536 bytes.
statusstring required
Snapshot lifecycle status. Known values: creating, ready, error.
Additional values may be introduced in future server versions.