> - A build system / package manager like Nix [1] but with a better user experience / more straightforward command-line tooling.

Working on it :)

> - A version control system which scales to petabytes or more. Something that I could put large video files in without thinking twice about it. Something a large company could use for their monorepo—or even their data warehouse.

https://github.com/facebookexperimental/eden

> A note-taking tool that allows me to organize notes in a graph with links between them

https://www.orgroam.com/