[Sevans711]

Closes #1795

Overview

Swaps to an algebraic transformation (node_lon = (node_lon - central_longitude + 180.0) % 360.0 - 180.0) to shift longitudes, instead of using cartopy.crs.PlateCarree(...).transform_points(...), to avoid cartopy.crs giving NaNs at the poles, which is what originally triggered #1795.

test_plot_with_nonzero_central_longitude() serves as a regression test for this. It loops across many cartopy projections using the new _cartopy_projections() helper function, which I just copy-pasted it directly from the uxarray_debug_utils I've been accumulating while developing uxarray. I know this helper function has more functionality than what is actually being used here, but rather than trim it down I think it is easier to just keep the full version for now, since it is just in the test suite and not user-facing?

Along the way, discovered a bug when applying _central_longitude_of() to ObliqueMercator projections. The previous behavior was to always silently return 0, ignoring any actually-input central_longitude. This PR fixes _central_longitude_of() to instead handle this case properly (regression test: test_central_longitude_of_for_all_nonlocal_projections()), and also to emit a warning instead of silently returning 0 when central_longitude cannot be determined (updated test_central_longitude_of_handles_cartopy_026_platecarree() accordingly, to check for such a warning).

PR Checklist

General

• An issue is created and linked
• Added appropriate labels (if your uxarray repo permissions allow it)
• Filled out Overview and Expected Usage (if applicable) sections

Testing & Benchmarking

• There is adequate test coverage of changes from this PR (add new tests if needed)
• [N/A] If this PR could affect performance, ran ASV benchmarks and confirmed they show expected behavior (add a new benchmark if necessary)

Documentation and Examples

• [N/A] Docstrings updated with any function changes, and included in all new functions
• [N/A] User (public) functions added to docs/api.rst; internal (private) function names start with an underscore (_)
• [N/A] If touched any notebook files, cleared the output of all cells before committing
• [N/A] If added new notebook files, put into appropriate directories and referenced in appropriate files

AI Disclosure

AI Usage: Some Claude to help with debugging, some GitHub Copilot's inline code suggestions.

• I have tested and take responsibility for all AI-generated content in my PR.