Summary

Brings the release pipeline to parity with backend.ai-go's packaging workflow so published artifacts are trusted by Gatekeeper and SmartScreen out of the box. All changes are confined to .github/workflows/release.yml.

macOS — added notarization after existing codesign

• Submit a ditto'd zip of the already-codesigned binary to xcrun notarytool submit --wait using the App Store Connect API key (AC_API_KEY_ID / AC_API_ISSUER_ID / AC_API_PRIVATE_KEY_P8 secrets — already configured in the packaging environment but previously unused).
• On Invalid/Rejected, fetch xcrun notarytool log <id> for diagnostics before failing the job.
• Verify with spctl --assess --type execute --verbose; treat ticket-propagation lag as a warning (not a hard failure) since Gatekeeper checks online at first launch regardless.
• Stapling is intentionally skipped. xcrun stapler only operates on .app/.dmg/.pkg containers, not on bare Mach-O executables. The notarization ticket lives on Apple's servers and Gatekeeper fetches it online — no offline ticket is needed for a single-binary CLI.
• API key file is written to $RUNNER_TEMP with chmod 600 and removed unconditionally via trap cleanup EXIT.

Windows — switched to self-hosted runner and added signtool

• Matrix entry os changed from windows-latest → windows-on-macmini02-x64, the same self-hosted runner used by backend.ai-go. Certificate is already installed in the Windows Certificate Store on that runner.
• Sign all-smi.exe with signtool sign /tr http://ts.ssl.com/ /td sha256 /fd sha256 /a before the Compress-Archive step so the released .zip contains the signed .exe.
• Verify with signtool verify /pa (warn-only — verification can lag right after signing on the timestamp authority).
• Pin CARGO_HOME / RUSTUP_HOME to C:\.cargo / C:\.rustup outside GITHUB_WORKSPACE so the registry survives workspace cleanup between jobs.
• Skip the actions/cache step on this runner since the persistent paths already handle caching; keeping it would only mirror an empty ~/.cargo.

Out of scope (per #242)

• No .pkg/.dmg installers for macOS (stays single-binary)
• No MSI/NSIS for Windows
• No changes to ci.yml (still runs on windows-latest)
• No changes to Linux/Homebrew/Debian PPA pipelines
• No source code changes

Test plan

This workflow only triggers on release: published and workflow_dispatch. Validation needs to happen on the next release or a manual dispatch:

• Trigger via workflow_dispatch against a draft tag (or wait for the next published release) and confirm:
  • macOS job: Notarize macOS binary step runs to completion with status: Accepted and spctl --assess reports the binary is trusted
  • Windows job: schedules onto windows-on-macmini02-x64 (not GitHub-hosted), Sign Windows binary with signtool step exits 0, signed all-smi-windows-x86_64.zip is uploaded
  • No secret values appear in workflow logs (GitHub auto-masks, but spot-check)
• After download:
  • On macOS: spctl --assess --verbose --type execute /path/to/all-smi reports accepted and Notarized Developer ID
  • On Windows: Get-AuthenticodeSignature .\all-smi.exe reports Valid with a non-expired timestamp
• Confirm Cache cargo step is skipped on the Windows job and present on the others

Closes #242