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/shortid.rs

@@ -9,8 +9,7 @@ use rand::RngExt;
 
 /// Base58 alphabet — Bitcoin-style. 0 / O / I / l are excluded
 /// because they are easily confused in print.
-const ALPHABET: &[u8; 58] =
-    b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+const ALPHABET: &[u8; 58] = b"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
 
 const DEFAULT_LEN: usize = 10;