Update text to recommend Python v3.10+

[tomodwyer]

As we have updated OpenSAFELY CLI to drop support for Python v3.8 and v3.9

opensafely-core/opensafely-cli#280

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[mikerkelly]

Thanks Thomas.

The supported opensafely-cli versions are now 3.10, 3.11, 3.12, and 3.13. that does not include Python 3.14, versions of which have been released since 2025-10.

Given that, I think it would be more helpful to state explicitly that versions between 3.10--3.13 are supported. As if someone has the most recent Python, 3.14, as we recommend, they will not be able to use it right now. That could be frustrating, because we told them something not true, and depending on their control over their system the install may not have been a trivial thing to do (for example, if they had to seek special permission to have 3.14 installed, only to find that this does not work, and they have to go back and ask again).

What do you think?

I think that is relevant to docs/install-python.md, and also README.md from opensafely-cli which recommends "at least version 3.10 but the more recent the better". I think that we should change both of those.

I don't think we should change docs/index.md, see comment.

[tomodwyer]

@mikerkelly I think I was being optimistic in hoping the Python v3.14 changes would be done before we would need to merge this, but you're right I'll add another PR in for that after this one.

[mikerkelly]

@mikerkelly I think I was being optimistic in hoping the Python v3.14 changes would be done before we would need to merge this, but you're right I'll add another PR in for that after this one.

Fair. I think that any "version X+" when we actually require a bounded range is hostage to any future release making it inaccurate without us noticing. So it might be best to always state the exact range. Would be nice if we could somehow configure that once as a variable and have it propagate in the docs, probably not worth it only if very quick though.

[tomodwyer]

Good point, we don't automatically support 3.15 when it's out.