Add sa_ct_interp and tracer_ct_interp functions to GSW-Python

[mauzey1]

This will add the MRST-PCHIP interpolation functions added to GSW-C in TEOS-10/GSW-C#73 to the Python library. This will also add the MRST interpolation method option from TEOS-10/GSW-C#74 to geo_strf_dyn_height.

[efiring]

Thank you for the great work! This is almost ready to merge. The pre-commit checker (ruff) has 3 complaints that will be trivial to fix:

gsw/interpolation.py:61:16: C419 Unnecessary list comprehension
gsw/interpolation.py:145:16: C419 Unnecessary list comprehension
gsw/tests/test_geostrophy.py:1:1: I001 [*] Import block is un-sorted or un-formatted

If you don't mind, I would like to see this merged as a single squashed commit. Let me know if that is OK, and if you would prefer to squash/rebase it yourself, or have me use one of the github merge options to do it.

[efiring]

@ocefpaf There are now several different modes of test failure, only one of which (the pre-commit ruff check) looks related to the content of the PR. Do you know what is going on? For example, I see micromamba.exe failing, a twine argument error, and perfectly good URLs being rejected by the link checker.

[ocefpaf]

. Do you know what is going on? For example, I see micromamba.exe failing, a twine argument error, and perfectly good URLs being rejected by the link checker.

• Micromamba 2.0.3 has a bug on Windows and they are looking into it. Ignore that one for now.
• I believe that the failing URLs may be a problem with latest curl 8.11 and redirects, not sure. Investigating in Fix URLs redirects #187 (It is not! The failures are due to another oddity in micromamba's solve for our development env.)
• Why we are getting twine 1.11.0 there is beyond my comprehension. Something is amiss latest micromamba.

TL;DR this PR is good to go with just the pre-commit fixes. I'm working on the rest a bit today and should finish tomorrow morning.

[efiring]

@mauzey1, looking at the output from a slow test (ubuntu-22.04 (aarch64) wheels), I noticed the following compiler warnings:

 gcc -pthread -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -fPIC -I/tmp/build-env-10xopuvh/lib/python3.13/site-packages/numpy/_core/include -I/project/src/c_gsw -I/tmp/build-env-10xopuvh/include -I/opt/_internal/cpython-3.13.0/include/python3.13 -c src/c_gsw/gsw_oceanographic_toolbox.c -o build/temp.linux-aarch64-cpython-313/src/c_gsw/gsw_oceanographic_toolbox.o
  src/c_gsw/gsw_oceanographic_toolbox.c: In function ‘gsw_sa_ct_interp’:
  src/c_gsw/gsw_oceanographic_toolbox.c:8642:16: warning: unused variable ‘j’ [-Wunused-variable]
   8642 |         int i, j, k, prof_len,
        |                ^
  src/c_gsw/gsw_oceanographic_toolbox.c: In function ‘gsw_tracer_ct_interp’:
  src/c_gsw/gsw_oceanographic_toolbox.c:11378:19: warning: unused variable ‘ct_f’ [-Wunused-variable]
  11378 |         double d, ct_f, unique_p, ct_sum, tracer_sum, min_p_obs, max_p_obs;
        |                   ^~~~
  src/c_gsw/gsw_oceanographic_toolbox.c:11375:24: warning: variable ‘i_2_len’ set but not used [-Wunused-but-set-variable]
  11375 |             i_out_len, i_2_len;
        |                        ^~~~~~~
  src/c_gsw/gsw_oceanographic_toolbox.c:11372:16: warning: unused variable ‘j’ [-Wunused-variable]
  11372 |         int i, j, k, prof_len,
        |                ^
  src/c_gsw/gsw_oceanographic_toolbox.c: In function ‘gsw_sa_ct_interp’:
  src/c_gsw/gsw_oceanographic_toolbox.c:8645:43: warning: ‘i_shallower’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   8645 |             i_out_len, i_2_len, i_frozen, i_shallower, i_above, i_above_i, i_below_i;
        |                                           ^~~~~~~~~~~

I would appreciate it if you would provide a PR to GSW-C and a commit to the current PR to clean up those warnings. Given that GSW-C now tests with several compilers, it is possible that additional warnings will turn up, but I don't expect that.

[ocefpaf]

Eric, @SylvainCorlay's team removed/yanked micromamba 2.0.3 and the CIs should work again as expected. I restart the jobs.