Buzz Desktop v0.5.4 macOS arm64 artifacts fail strict code-sign validation

# Buzz Desktop v0.5.4 macOS arm64 signature blocker

The official [Buzz Desktop v0.5.4 release](https://github.com/block/buzz/releases/tag/desktop-v0.5.4) cannot currently be installed on Apple Silicon under a strict signed-release policy.

We independently downloaded both official macOS arm64 formats from that release:

- the disk image;
- the application updater archive.

Both downloads match the identities published by GitHub. Both contain the same application executable and report the expected version, architecture, developer team, hardened runtime, and stapled notarization metadata.

However, strict macOS code-sign validation fails for the application and its main executable in both formats with this result:

```text
invalid signature (code or signature have been modified)
In architecture: arm64
```

The currently installed Buzz Desktop v0.5.3 application passes the same strict validation on the same host, so this is specific to the v0.5.4 release artifacts rather than a general verifier failure.

No v0.5.4 artifact was installed, modified, locally re-signed, or allowed through a security bypass.

Please publish a corrected official macOS arm64 artifact, or a replacement immutable release, whose extracted application passes strict macOS code-sign and Gatekeeper verification. Once available, we can re-run the release and rollback checks and complete the update.