Publish signed app zip for the next release

[rain2day]

Goal

Create a repeatable release packaging path for Codex Pet Meter so users can download a built app without running the installer from source.

Scope

• Decide whether the first artifact should be an ad-hoc signed zip, notarized zip, or source-only release note.
• Document the packaging command.
• Add checksum generation if a binary artifact is uploaded.
• Keep the current source install flow working.

Done When

• Release packaging steps are documented in docs/MAINTAINER_WORKFLOWS.md.
• The next release includes either a verified artifact or a clear note explaining source-only distribution.