Fix CI: remove explicit x64 arch to support Apple Silicon macOS runners

[dependabot]

The macOS-latest GitHub Actions runner now provisions Apple Silicon (arm64) machines. The CI workflow had arch: x64 hardcoded in the matrix, causing julia-actions/setup-julia to fail with an architecture mismatch error.

Changes Made

• Removed the arch dimension from the CI matrix (was - x64)
• Removed the explicit arch input from the julia-actions/setup-julia step so it auto-detects the correct architecture (x64 on Linux/Windows, aarch64 on macOS)
• Removed arch: x64 from the include entry for the Julia 1.10 minimum version job
• Updated the job name template to drop the ${{ matrix.arch }} component

Note
Automatic rebases have been disabled on this pull request as it has been open for over 30 days.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.09%. Comparing base (6675b01) to head (d92aabf).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #136   +/-   ##
=======================================
  Coverage   74.09%   74.09%           
=======================================
  Files          15       15           
  Lines        1521     1521           
=======================================
  Hits         1127     1127           
  Misses        394      394           

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