Update Buffer.kt

[GeorgCantor]

Reduced Complexity: The previous nested if statements for calculating the width were replaced with a single when expression.

[JakeWharton]

This change slows down the code, changing it from a biased binary search to a linear scan. We're actually going to change it to a constant time operation, I just haven't gotten around to it yet. See https://www.romainguy.dev/posts/2024/down-another-rabbit-hole/