* fix(release): attach the snap to GitHub Releases
v0.17.0 packed the snap, then Store review of uinput failed the job, so
the file never reached the tag. Build and attach first. A Store hold is
a warning, not a failed release. SHA256SUMS covers the .snap.
snap-backfill.yml rebuilds an existing tag, appends the snap to the
manifest, and attests only that file.
* fix(release): keep snap tags out of the shell and fail real Store errors
Pass the tag through the environment like verify-release.yml. Treat only
an allow-installation review as a successful Store publish. snap-backfill
runs verify_release.py after it rewrites SHA256SUMS.
* style(test): format snap-backfill shell-injection guard with black
