update installation instructions, add test for macOS

[jgraeb]

• Updated the installation instructions for macOS with and without conda in the docs and the readme.
• One issue remaining is that the test using pdm (and not conda) on macOS does not successfully run (test_pdm_env_macos.yaml) because of the pygraphviz installation. In the conda env (where pygraphviz is installed using conda), pdm finds graphviz successfully, but when pygraphviz is installed using pip, pdm does not find it and errors out. Any ideas on why this could be?

[slivingston]

@jgraeb looks like the cache is broken again. I will investigate.

[jgraeb]

@slivingston It seems like the conda tests are now broken too when gurobipy is installed via pdm, which worked well before. Could this have to do with the cache as well?
Edit: It is also the exact same error for the macOS and ubuntu pdm tests.

[slivingston]

I deleted recent cache entries and retried one of the macOS jobs, and it passed: https://github.com/tulip-control/floras/actions/runs/11296986960/job/31423297240

As for the workflows with conda failing, I do not expect the cache is the cause because the workflow file does not involve the cached Spot files. My best guess is that pdm install or the PDM lock file are not being used correctly. The error messages refers to the hash of gurobipy, which I expect is comparing the hash value in the lock file with the package file, either downloaded or from the cache that the PDM GitHub action or from a cache created by the miniconda GitHub Action, if any

[slivingston]

Python 3.13 was just released on Friday, 7 October, and I notice that:

• The failed workflows with conda show a path that indicates Python 3.13 is being used.
• The most recent passing workflow with conda was on 7 October, perhaps before the Python 3.13 version became part of the conda release: https://github.com/tulip-control/floras/actions/runs/11220743800/job/31189563981
• gurobipy is not supported on Python 3.13 yet because none of the release files on PyPI are built for it and the upstream documentation only refers up to Python 3.12.

I think the key problem is that the conda workflows are using the unintended Python 3.13.

[jgraeb]

@slivingston Great, deleting the cached files and updating the conda setup fixed most of the tests again. But we are now back to the original error involving pdm and pygraphviz in a conda environment, but now for ubuntu and macOS and only in python version 3.12 (3.10 and 3.11 in the same workflow run fine). Pygraphviz 1.14 should work with python 3.12 and it gets installed but pdm cannot find the header file (error message).