The imsd repo's package CI is now the only producer of the imsd apk. The
image installs the exact registry package users get via 'apk upgrade'
(pinned version + sha256 of the registry files), so the two can no longer
diverge and the payload-parity rule between two packagings is gone.
pmbootstrap has no knob for a third-party repository, and after the main
'apk add' it re-adds every package in its local packages dir by file path,
which makes apk verify the package's own signature. Registry packages are
signed with per-run keys nobody keeps (phones trust the registry-signed
index), so apk-resign.py replaces the signature stream with one from this
run's abuild key; control and data streams stay byte-identical and the
identity checksum equals the registry's. Verified on the host with apk
3.0.8: originals UNTRUSTED, re-signed OK, checksums equal.
The publish step skips imsd-*: those files came from the registry.