Add MATLAB MEX CI for set_path / level_solver.cpp

[phflot]

Summary

Add a GitHub Actions workflow that verifies that set_path can compile the MEX target core/level_solver.cpp across supported MATLAB releases and platforms.

This is needed before patching the reported macOS arm64 / R2024b linker issue, so we can distinguish regressions in the toolbox from MATLAB/Xcode compatibility problems.

Proposed workflow

Add a GitHub Actions workflow, for example .github/workflows/matlab-mex.yml, that:

• checks out the repository
• installs MATLAB using MathWorks GitHub Actions
• runs mex -setup C++
• runs set_path
• verifies that the expected MEX binary is created or loadable

Initial matrix:

• MATLAB: R2024b, R2025b
• OS: ubuntu-latest, windows-latest, macos-26 if available
• architecture: especially macOS arm64, where possible

Acceptance criteria

• A MATLAB CI workflow exists and runs on pull requests and pushes.
• The workflow exercises set_path rather than only MATLAB path setup.
• The workflow fails if core/level_solver.cpp cannot be compiled.
• The workflow prints enough diagnostic information to debug failures:
  • MATLAB version
  • computer
  • mexext
  • selected C++ compiler
  • macOS/Xcode version on macOS runners
• The known problematic R2024b + newer Xcode/macOS configuration is either:
  • reproduced as a failing diagnostic job, or
  • marked explicitly as an expected/allowed failure until the compatibility fallback is implemented.

Follow-up

After this CI issue is complete, add a guarded compatibility fallback in core/make.m for affected MATLAB/Xcode/macOS combinations.

[ehennestad]

I added a workflow here for testing set_path across different macOS and MATLAB releases here:
https://github.com/ehennestad/flow_registration/blob/main/.github/workflows/flowreg-setpath-smoke.yaml

The same error that I reported in issue #31 seems to be occurring macOS-26 across MATLAB R2023b-R2025a. See the actions run here:
https://github.com/ehennestad/flow_registration/actions/runs/25340150527

Feel free to copy that workflow if it is useful!

[phflot]

Dear Eivind,
Thank you! I hope the license and compile issues are not too time-critical for you, as I'll be a bit busy over the next two weeks.
Once I have updated the license, I’ll also add short instructions for contributions and PRs - If you are interested, you are welcome to open one with the workflows and contribute to the main branch.
Best wishes,
Philipp