You might be interested in checking out Advent of Code (https://adventofcode.com/) to exercise your language. I had fun doing that with mine.

Also, there is a programming language development discord if that's your thing and you want to discuss your project with like-minded folks: https://discord.com/invite/4Kjt3ZE

> No tooling (LSP, debugger, etc.)

If you don't want to do a full LSP yet, you can get far with simple highlighting and scraping the output of the compiler for errors. I'm also dumping some additional information (top level names / types) as json to facilitate completion and type on hover.

> Is context-oriented programming solving a real problem or creating busywork?

Not sure. This kind of reminds me of dynamic scoping, something that seems to come up in languages that don't support. Go pushes contexts through as additional arguments, and Java thread local variables cover cases that look like dynamic scoping to me.

> Should I focus on making it fast OR making the stdlib useful?

I would go with whatever sounds fun and interesting to you. You'll probably want examples of what you want to make faster if you go with the former.

> Is 1-based indexing a dealbreaker for you?

Not a huge deal, but that was surprising to me in Lua. I adapted to it, but it did cause a little bit of awkwardness in some code I wrote that decoded a binary file format (realm database).

> Would arbitrary precision by default bother you for a general-purpose language?

I only glanced at it, but it looks like the user can choose IEEE if they want. It's nice to have options and few languages have this option.