[WIP] Nexus: Packaging and Supported Versions

[brockdyer03]

Proposed changes

This PR is designed to make Nexus available to install via a package manager such as pip or uv.

The general changes include:

• Adding a pyproject.toml file with minimum supported versions
• Creating a build of Nexus with uv
• Rewriting the Nexus README (now in markdown, name changed to README.md)
• Rewriting the Nexus install instructions to add install methods via a package manager (will not remove previous install instructions)

What type(s) of changes does this code introduce?

• New feature
• Refactoring (no functional changes, no api changes)
• Documentation or build script changes

Does this introduce a breaking change?

• Yes
• No

What systems has this change been tested on?

Laptop running Fedora 43 with uv 0.9.24 and Python 3.14.2
Docker container of Ubuntu 18.04 with pip 21.3.1 and Python 3.6
Note: The default install of pip on Ubuntu 18.04 is pip 9.1, which does not work to install via GitHub links. The minimum version of pip that will do this is 10.0.0. I have tested and can confirm that running python3 -m pip install -U pip with Python 3.6 will update pip to version 21.3.1, which does work.

Checklist

• • I have read the pull request guidance and develop docs
• • This PR is up to date with the current state of 'develop'
• • Documentation has been added (if appropriate)

[prckent]

Thanks Brock. Q. Are you done with updates including updating the readme and install instructions? If so, please add the [x] to the 3rd and 4th bullets in the PR description and I will take a look.

[brockdyer03]

I'm not quite done. After a chat with @jtkrogel yesterday I realized that perhaps there should be some additional clarification for users, and most likely a note about selecting a branch to install.

The current default is @develop, however it may be prudent to switch that to @main, although that becomes complicated because @main won't be available until the next release.

Additionally, I still need to update the Nexus docs, since that will likely be where people go for install instructions, not the readme.