Publish platform binaries to package manager on release

Problem

Step Runner's releases page lists binaries as available for download, but no binaries are actually published to releases. This affects all platforms.

Solution

We need to publish Step Runner binaries for all supported platforms to the releases page. The following platform binaries should be included:

macOS (darwin):

• step-runner-darwin-amd64
• step-runner-darwin-arm64

FreeBSD:

• step-runner-freebsd-amd64
• step-runner-freebsd-arm64
• step-runner-freebsd-386
• step-runner-freebsd-arm

Linux:

• step-runner-linux-amd64
• step-runner-linux-arm64
• step-runner-linux-arm
• step-runner-linux-s390x
• step-runner-linux-ppc64le
• step-runner-linux-386

Windows:

• step-runner-windows-amd64.exe
• step-runner-windows-386.exe

Implementation Steps

1. Restore the binary upload process for all platforms
2. Ensure binaries are actually published to the releases page as advertised
3. Update release documentation if needed

Context

• Windows binary uploads were reverted in !269 (merged) due to build/functionality issues
• !309 (merged) fixed the underlying Windows compatibility problems
• This enhancement will ensure the releases page accurately reflects available downloads and expand Step Runner's platform support