Refs #1.
`scripts/install-apt.sh` explained the sqv rejection as a malformed MPI
encoding in an Ed25519 key. The registry does not serve one: at
`api/packages/heavy-duty/debian/repository.key`, `gpg --list-packets`
reports `algo 1` (RSA) with a 2048-bit `pkey[0]`. The explanation was
therefore wrong about the only part of itself that was checkable.
The comment now states the measurement and points at #1 for the cause,
rather than naming a mechanism nobody verified. This satisfies #1's
criterion that `git grep -in 25519` return no hits outside test fixtures,
which it now does.
Behaviour is unchanged: this commit edits a comment. The automatic
fallback this file still performs contradicts ruling B and is NOT fixed
here — that work is still owed on !38.
