Entire

Done. Committed (not pushed).

Bottom line: Of ~16 open nitpicks, only one was a real issue worth fixing — the rest were already-fixed, false, or theoretical.

Fixed (commit b82a741ef26):

Added t.Parallel() to all 10 cross-juris transport tests. Copilot's stated reason was wrong (tparallel lint failure — lint passes 0 issues, and paralleltest isn't even enabled), but the repo's own CLAUDE.md mandates t.Parallel() and the sibling client_test.go follows it. Tests own their httptest servers/transports with no process-global state, so safe. Green under -race.

Declined — all genuinely non-issues:

Host port/casing mismatch (cursor): both sides come from the same JURISDICTION_AUTH_HOSTS config, byte-identical. Canonicalizing would diverge from the entiredb twin. toothbrush's reasoning holds.
MaxBytesReader panic (Copilot): false — nil writer fails the requestTooLarger type assertion, so it's a no-op, not a panic.
drainAndRestoreBody no restore-on-error (Copilot, the refined re-take): unreachable in practice (8–64 KiB caps on tiny envelopes) and harmless when hit (read error = dead connection); the doc describes the success contract.
validateExchangeURL exact-path (Copilot): pure defense-in-depth — same-origin+https already gates JWT exposure; a bad path just makes the exchange fail gracefully.

Already addressed before this session: the three -race shared-slice comments (fixed via authRecorder in 6a23ba488ac).

You'll want to push and optionally reply to the declined threads — I left those for you.