release: open the Sigil bootstrap channel for v0.1.0

Replace both `unconfigured` trust pins in one commit, which is the only shape
`verify-sigil-bootstrap.py` accepts: it treats a half-configured channel as an
error rather than a partial rollout, so the repository key and the bootstrap's
embedded key and tag move together or not at all.

- `release/sigil-minisign.pub` becomes the offline Minisign public key
  3247504746CF2DB4. The private half was generated off-runner, is passphrase
  protected, and never enters CI: `Sigil Release` builds an unsigned draft,
  the operator signs it offline, and `promote-signed-draft` verifies that
  detached signature against this file as checked out from the tag.
- `website/install-sigil` pins the same key and `release_tag=v0.1.0`, so the
  public bootstrap installs exactly one immutable tag verified against exactly
  one key.

`sigil_bootstrap_verification=ok`, `sigil_bootstrap_channel=open`,
`website_static_gate=ok`, `portal_release_tests=ok`, 29/29 shell tests.

Do not merge to main until v0.1.0 is promoted. A merge deploys goq.sh, and the
install command would then point at a release that does not exist yet.

commit

8eb315666b1e1ba77f592549020e5bfdf4a670aa

parent

5c6fb7357de7484fddf43c5963ea781494f30c7d

author

Dami <dami.etoile@gmail.com>