It's basically what you're building, but more low-level. Really cool, to be honest -- serves the same market too. Do you have any significant differentiator, other than charts?
TextQuery actually uses DuckDB under the hood :) DuckDB is no doubt an excellent piece of software already. The differentiator is that GUI client is just a good lever to make many things easier.
In context of TextQuery: you can use tabs you can work on multiple queries. With Table editor you can edit multiple field values at once. During import, you can have better control over what the final table would look like (select/deselect columns, define data/time format etc.)
Again, it's a personal preference. Some people swear by psql, and some can't live without TablePlus/Postico.
It's basically what you're building, but more low-level. Really cool, to be honest -- serves the same market too. Do you have any significant differentiator, other than charts?