Map Units waveform metadata to waveforms

[ehennestad]

Motivation

This change fixes a mismatch between the NWB schema and the PyNWB Units mapper for waveform metadata.

The schema defines sampling_rate and unit attributes on waveform_mean, waveform_sd, and waveforms, but PyNWB only propagated Units.waveform_rate and Units.waveform_unit to waveform_mean and waveform_sd. As a result, a Units table containing only waveforms would lose waveform sampling metadata on write, and waveform_rate would not round-trip on read.

Fix #2182.

What changed

• Extend the write-side VectorData mapper so Units.waveform_rate and Units.waveform_unit are also written to the waveforms column attributes.
• Extend the read-side UnitsMap logic so it also considers waveforms when reconstructing waveform metadata.
• Add an integration test that round-trips a Units table with only waveforms and verifies both the in-memory metadata and the on-disk attributes.

How to test the behavior?

PYTHONPATH=src python -m unittest tests.integration.hdf5.test_misc.TestUnitsWaveformsOnlyIO tests.integration.hdf5.test_misc.TestUnitsIO

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running ruff check . && codespell from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

Prepared with Codex.

[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.13%. Comparing base (a2d1efa) to head (9af2788).

Files with missing lines	Patch %	Lines
src/pynwb/io/misc.py	55.55%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2183      +/-   ##
==========================================
+ Coverage   95.10%   95.13%   +0.03%     
==========================================
  Files          29       29              
  Lines        2943     2941       -2     
  Branches      443      441       -2     
==========================================
- Hits         2799     2798       -1     
- Misses         86       87       +1     
+ Partials       58       56       -2     

Flag	Coverage Δ
integration	72.86% <60.00%> (+0.01%)	⬆️
unit	85.41% <0.00%> (+0.05%)	⬆️

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