Decode a job-array membership from an instance's tags, or undefined if the instance carries no spawn:job-array-id. Mirrors the job-array branch of the Go describe path (pkg/aws/client.go). Malformed numeric tags fall back to 0.
Decode a job-array membership from an instance's tags, or undefined if the instance carries no spawn:job-array-id. Mirrors the job-array branch of the Go describe path (pkg/aws/client.go). Malformed numeric tags fall back to 0.