Well, here's what Fable came up with in 499 bytes of R in about half an hour: https://pastebin.com/sBsiGD9t, result: https://imgur.com/a/W3eDdIC. Probably with sitting down and tweaking you could do even better, but I think this is a decent first start.
Fable did that, I pretty much just told it to find the best Fourier sum which can draw a map of the world in less than 500 bytes of R. It downloaded geo data and made the curves to fit that on its own.
Can you post the unencode version? It would be nice to see the vector with the data, for example to count how many coefficients each continent got.
Have you tried with Bezier curves? Your images show a lot of pointy parts, like Southeast Asia and that usually needs a lot of high frequencies in the Fourier representation, so I think something piecewise may be better. (Perhaps a polygon is better.)
In its defense, it actually asked me whether I wanted to spend my 500 bytes on more resolution for the main continents or more landmasses, and I opted for the former. You can blame me for that, not Claude :)
Can the it also split Africa/Arabia/Eurasia?
Who/how decided which islands to keep and which to erase?
If you want to save a few characters, you can replace `length(v)` with the actual number.