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/mod.rs

@@ -21,9 +21,9 @@ pub mod walker;
 
 pub use action::ReferentialAction;
 pub use command::{
-    AlterTableAction, AppCommand, ChangeColumnMode, ColumnSpec, Command, CompareOp, CopyScope, Expr,
-    IndexSelector, MessagesValue, ModeValue, Operand, Predicate, RelationshipSelector, RowFilter,
-    ShowListKind, SqlForeignKey,
+    AlterTableAction, AppCommand, ChangeColumnMode, ColumnSpec, Command, CompareOp, CopyScope,
+    Expr, IndexSelector, MessagesValue, ModeValue, Operand, Predicate, RelationshipSelector,
+    RowFilter, ShowListKind, SqlForeignKey,
 };
 pub use parser::{ParseError, parse_command};
 pub use types::Type;