Ports change to json2csv from v4 to v5

[nfahlgren]

Describe your changes
In the v5 development branch, json2csv moved from the deprecated utils subpackage to the plantcv core package. This PR ports changes introduce in #1967 to the v5 branch.

Type of update
Is this a: update

For the reviewer
See this page for instructions on how to review the pull request.

• PR functionality reviewed in a Jupyter Notebook
• All tests pass
• Test coverage remains 100%
• Documentation tested
• New documentation pages added to plantcv/mkdocs.yml
• Changes to function input/output signatures added to updating.md
• Code reviewed
• PR approved

[deepsource-io]

DeepSource Code Review

We reviewed changes in 6d55522...0ff4ba6 on this pull request. Below is the summary for the review, and you can see the individual issues we found as inline review comments.

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PR Report Card

Overall Grade

Security   Reliability   Complexity   Hygiene   Coverage

Code Review Summary

Analyzer	Status	Updated (UTC)	Details
Python		Jul 13, 2026 4:06p.m.	Review ↗
Code coverage		Jul 13, 2026 4:06p.m.	Review ↗

Code Coverage Summary

Language	Line Coverage (New Code)	Line Coverage (Overall)
Aggregate	100% [✓ above threshold]	100%
Python	100% [✓ above threshold]	100%

➟ Additional coverage metrics may have been reported. See full coverage report ↗

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[joshqsumner]

Happy to have the change ported but it is a little redundant with some of the changes I made in parallel (I think this was me but I haven't blamed it)

line 95 of plantcv.parallel.run_parallel is

json2csv(config.results, os.path.splitext(config.results)[0])

So the extension is never used when running parallel anymore anyway. It's better for the specific tool to do this I think since you might call json2csv manually but if you want I can remove the call to os.path.splitext from run_parallel for a little less redundancy. @nfahlgren , would you like me to edit run_parallel as part of this?

[joshqsumner]

looks good