ci(release): add canary triggered after release workflow

[drew]

Summary

• Adds a new acceptance-test.yml GitHub Actions workflow that runs automatically after Release Dev and Release Tag workflows complete successfully
• Installs the CLI from the corresponding GitHub release artifact and runs openshell sandbox create --no-keep --no-tty -- echo "hello world" as a smoke test
• Tests both amd64 and arm64 architectures in parallel using a matrix strategy

Test Plan

• Workflow will trigger automatically on the next successful release (dev or tag)
• Validates the released CLI binary can be installed and execute a basic sandbox operation end-to-end