Spawn via $PATH 4: Updated docs & misc clean up

[teh-cmc]

Last one.

Spawn via $PATH series:

• Spawn via $PATH 1: Rust implementation #3996
• Spawn via $PATH 2: Redesign clap integration and clean up all examples #3997
• Spawn via $PATH 3: C and C++ implementations #3998
• Spawn via $PATH 4: Updated docs & misc clean up #4013

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested demo.rerun.io (if applicable)
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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