Add ARM64 container builds when open-sourced

[birdmanmandbir]

Summary

Currently we only build linux/amd64 container images to avoid slow QEMU emulation on GitHub Actions.

Context

• Native ARM64 runners are free for public repositories only
• Private repos require paid "larger runners" for native ARM64 builds
• QEMU emulation (building ARM64 on x64 runners) adds 10-30+ minutes to builds

Action Items

When/if this project is open-sourced:

1. Update .github/workflows/release.yaml to use native ARM64 runner:

   platforms: linux/amd64,linux/arm64

2. Consider using a matrix build with native runners for each architecture for best performance:

   jobs:
     build:
       strategy:
         matrix:
           include:
             - platform: linux/amd64
               runner: ubuntu-latest
             - platform: linux/arm64
               runner: ubuntu-24.04-arm

References

• GitHub ARM64 runners for public repos
• Native ARM64 vs QEMU performance