CI failure: Julia 1.6 tests failing on macOS-latest (ARM64 runner)

[amemya]

Summary
The CI job for Julia 1.6 on macOS is currently failing.
This appears to be due to macos-latest updating to Apple Silicon (ARM64) runners, while Julia 1.6 does not provide official binaries for macOS ARM64.

1.6 - macOS-latest - x64

Run julia-actions/setup-julia@v1
  with:
    version: 1.6
    include-all-prereleases: false
    arch: ARM64
    show-versioninfo: false

(Note: Julia 1.6 only supports x86_64 on macOS.)

Proposed Solution
Update the workflow file (.github/workflows/runtests.yml) to explicitly request the x64 architecture for macOS runners, or use an Intel-based runner (e.g., macos-13) for older Julia versions.

Action Plan
I am working on a fix and will open a PR shortly.