Block header context the challenge is anchored to.
Starting nonce offset. number | string (audit L-4): btxd's nonce64 is a full u64; values > 2^53 lose precision as a JS number, so btxd may emit it as a decimal string. BigInt() (in the solvers) accepts either form.
number | string
nonce64
number
BigInt()
Block header context the challenge is anchored to.