I'm a happy user of Obsidian as other users have commented, but I must say having your Notes + IDE on the same app has its perks.

I applied but submitted my code challenge, I must say being already familiar with TypeScript/React code bases and being a heavy user of VSCode, I don't know why, but after a few months passed I found again the code challenge in my mail and just did it in an hour or so, it was really easy to set up, iterate with, and develop what was asked for.

I think it's a big enough market to have several winners, would hope so at least! should look into how to share files in between them all