Get the single value of a scalar tag parsed as a base-10 integer, or undefined if missing.
The Proof secret.
Tag key to lookup.
A present value that is not a safe base-10 integer throws rather than reading as absent, so a caller's default never replaces a malformed condition.
If the tag carries more than one value, or a value that is not a safe integer.
Get the single value of a scalar tag parsed as a base-10 integer, or undefined if missing.