JSON.parse rounds a number past 2**53, so a listing seed such as
9223372036854788153 reached the page as 9223372036854788000 while the
inspector showed the file's digits. Every non-null card seed is now its
decimal string.
The Node parity harness now JSON.parses the real listing response and
compares String(seed) with the seed the inspector shows, including a
seed past 2**53. TESTING.md describes the string contract and drops the
removed exact re-read.