style: format the whole tree with cargo fmt (stock defaults, #35)

One-time, mechanical reformat — no functional changes. The tree was not
rustfmt-clean (~1800 hunks across ~100 files); this brings it to stock
`cargo fmt` defaults so a `cargo fmt --check` CI gate can follow.
Behaviour-preserving: 2509 pass / 0 fail / 1 ignored (unchanged baseline),
clippy clean. A .git-blame-ignore-revs entry follows so `git blame`
skips this commit.

src/dsl/walker/lex_helpers.rs

@@ -110,9 +110,7 @@ pub fn consume_number_literal(source: &str, start: usize) -> Option<(usize, usiz
         return None;
     }
     let mut i = start;
-    let leading_minus = bytes[i] == b'-'
-        && i + 1 < bytes.len()
-        && bytes[i + 1].is_ascii_digit();
+    let leading_minus = bytes[i] == b'-' && i + 1 < bytes.len() && bytes[i + 1].is_ascii_digit();
     if leading_minus {
         i += 1;
     }