Add carbon molar mass physical constant

[SeanBryan51]

This change replaces the magic number 1.201e-5 with a carbon molar mass constant (units: $\mu g / mol$) in the cable output module.

Type of change

Please delete options that are not relevant.

• New or updated documentation

Checklist

• The new content is accessible and located in the appropriate section
• I have checked that links are valid and point to the intended content
• I have checked my code/text and corrected any misspellings

Testing

• Are the changes bitwise-compatible with the main branch? If working on an optional feature, are the results bitwise-compatible when this feature is off? If yes, copy benchcab output showing successful completion of the bitwise compatibility tests or equivalent results below this line.

2026-02-23 17:04:18,445 - INFO - benchcab.benchcab.py:380 - Running comparison tasks...
2026-02-23 17:04:18,472 - INFO - benchcab.benchcab.py:381 - tasks: 168 (models: 2, sites: 42, science configurations: 4)
2026-02-23 17:07:09,718 - INFO - benchcab.benchcab.py:391 - 0 failed, 168 passed

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📚 Documentation preview 📚: https://cable--687.org.readthedocs.build/en/687/

[bschroeter]

Functionally approved, however, I question why we are keeping commented code in the source? Is there a reason why it is still there?

[SeanBryan51]

Thanks Ben

I question why we are keeping commented code in the source? Is there a reason why it is still there?

The comments will be removed in #688 🙂

[SeanBryan51]

As benchcab doesn't currently enable CASA-CNP, I've manually tested a CASA run using these scripts: https://github.com/SeanBryan51/crujra_accessN96_1h/tree/casa-cnp-configuration-serial - results are bitwise identical to main