Fix tutorial bug - sampling interval of the input PDF (0.1047...) is larger than the Nyquist interval (0.10471975...)

[bobleesj]

Problem

The following tutorial example

srmise data/Ag_nyquist_qmax30.gr --plot --range 2 3.5
    --baseline "Polynomial(degree=1)"

gives the following error message:

(diffpy.srmise_env) macbook@Macbook-Air-327 examples % srmise data/Ag_nyquist_qmax30.gr --plot --range 2 3.5
    --baseline "Polynomial(degree=1)"
The input PDF appears to be missing information: The sampling interval of the input PDF (0.10471976036036036) is larger than the Nyquist interval (0.10471975511965977) defined by qmax=30.0.  This information is irretrievable.
Traceback (most recent call last):
  File "/Users/macbook/miniconda3/envs/diffpy.srmise_env/bin/srmise", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/Users/macbook/miniconda3/envs/diffpy.srmise_env/lib/python3.13/site-packages/diffpy/srmise/applications/extract.py", line 537, in main
    cov = ext.extract()
  File "/Users/macbook/miniconda3/envs/diffpy.srmise_env/lib/python3.13/site-packages/diffpy/srmise/pdfpeakextraction.py", line 417, in extract
    pe.extract_single()
    ~~~~~~~~~~~~~~~~~^^
  File "/Users/macbook/miniconda3/envs/diffpy.srmise_env/lib/python3.13/site-packages/diffpy/srmise/peakextraction.py", line 853, in extract_single
    for step in dclusters:
                ^^^^^^^^^
  File "/Users/macbook/miniconda3/envs/diffpy.srmise_env/lib/python3.13/site-packages/diffpy/srmise/dataclusters.py", line 208, in __next__
    if test_idx < self.clusters[nearest_cluster[0], 0]:
                  ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices
zsh: command not found: --baseline

Proposed solution

It could be based on comparing two numbers that are meant to be identical but slightly different in values.

[bobleesj]

Tutorial link: https://www.diffpy.org/diffpy.srmise/tutorial/extract_single_peak.html

[sbillinge]

When we fix this we could maybe also make sure that we use Andrew's whittaker-shannon interpolation function in diffpy-utils. Since this is Andew's baby it is also possible that he made this switch already and this is causing the break?