fix: tokenize group/signature/Future paths with regex

[phrwlk]

Motivation

Logos #[token] attributes only match exact string literals and do not interpret regex metacharacters. The existing definitions for group::, signature::, and Future::* used #[token(r"...[a-zA-Z]...")] and never matched real code like group::GEN, signature::verify, or Future::await. These paths were then not classified as IdVariants::Path, which the grammar expects for associated constants and associated function calls.