Suggestion: rename "arc length parameterization" to "unit speed parameterization"

[rhinopotamus]

This came up in a thread on bluesky the other day. These two terms are synonymous and I have it on good authority (TJ Hitchman lol) that the actual differential geometers use them interchangeably.

If this sounds interesting I can take a crack at rewriting the text of 9.8 to see if this, like, works at all.

[mitchkeller]

Good news! Nick was already redrafting with language in this direction since it's what he uses when he teaches. We hopefully will have a working draft this semester that we'll share with you on this issue for feedback.