gh-289: Adding new tracer class PositionsTracer_Weyl_GGL and PositionsTracer_Weyl_GC

[NastassiaG]

🚀 Pull Request Checklist

✅ Summary

This PR adds new Weyl-specific PositionsTracer classes, enabling a model-independent measurement of the Weyl potential.

🔄 Changes

• cloelib/observables/photo_Weyl.py (new): adds two new Weyl tracer classes.
• cloelib/cosmology/Weyl_cosmology.py (new): adds a wrapper class that applies a non-linear boost to a power spectrum at fixed z_ini.
• cloelib/summary_statistics/angular_two_point.py (small modifications): checks based on type(...) are not compatible with subclasses of PositionsTracer, so an isinstance(...) fallback was added for compatibility with the new Weyl tracer classes.
• Updated the perturbations and observables documentation to include the new classes.

🛠 How to Test

A dedicated playground branch (called as well 289-PositionsTracerWeyl) has been used to test these changes extensively, including:

• Initializing instances of both new classes, PositionsTracer_Weyl_GGL and PositionsTracer_Weyl_GC, with various settings.
• Computing angular power spectra for GC and GGL using the new tracer classes.
• Comparing the Weyl and standard positions tracer classes at the level of both window functions and angular power spectra.

📝 Documentation

• This PR updates documentation
• This PR does not require documentation changes
• Issue created for documentation update: Don't forget to link the task!

🏗 Related Issues

Resolves #289

📌 Additional Notes

A follow-up PR will include Weyl-specific EuclidLikelihood classes in cloelike and, if appropriate, merge the playground branch into main.

✅ PR Checklist for Developers

• I have titled this PR before merging as "gh-#:", where "#" represents the task it closes
• I have run locally pre-commit using pre-commit run --all-files
• I have tested my changes locally
• No new warnings or errors introduced
• I have updated documentation (if applicable)
• My changes do not introduce breaking changes (i.e: the package still gets installed)
• I have added unit tests (if applicable)
• I have consistently updated the GitHub information for the project, including milestones, task types, and other relevant details.

✅ PR Checklist for Reviewers

• The next PR targets the correct branch
• CI tests have run and passed for the latest commit on the source branch
• Check that the code can still be installed if new packages are imported
• If necessary, the notebooks in the playground will be updated in a corresponding follow-up PR
• Coverage percentage is retained or increased
• Quality of new/changed code is acceptable
• Quality of new/changed unit tests is acceptable
• No data files have been included in the commits
• Implementation follows the agreed task description point by point
• Check that any added folder/file has been added to the README.md file
• Check that the documentation has been updated accordantly
• Check that the corresponding branch has been deleted after merging. If not, delete it

[NastassiaG]

@cloe-org/cloe-maintainers I believe this branch is in good shape. It has two new files and one changed file. I've grouped them all into one draft PR, since they're all related to the new Weyl PositionsTracer classes, but let me know if you prefer to split them into various PRs. Also, let us know if unit tests are required for this - if yes, maybe @zsirap could look into it ?