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.

tests/it/column_op_guards.rs

@@ -24,8 +24,7 @@ fn rt() -> tokio::runtime::Runtime {
 
 fn open() -> (project::Project, Database, tempfile::TempDir) {
     let dir = tempfile::tempdir().expect("create tempdir");
-    let project =
-        project::open_or_create(None, Some(dir.path())).expect("open or create project");
+    let project = project::open_or_create(None, Some(dir.path())).expect("open or create project");
     let persistence = Persistence::new(project.path().to_path_buf());
     let db = Database::open_with_persistence_and_undo(project.db_path(), persistence, true)
         .expect("open db with persistence");
@@ -48,7 +47,9 @@ fn make_t_with_check(db: &Database, r: &tokio::runtime::Runtime) {
         vec!["a < b".to_string()],
         vec![],
         false,
-        Some("create table T (id int primary key, a int, b int, c text, check (a < b))".to_string()),
+        Some(
+            "create table T (id int primary key, a int, b int, c text, check (a < b))".to_string(),
+        ),
     ))
     .expect("create T with table CHECK");
 }
@@ -285,7 +286,10 @@ fn drop_column_covered_by_a_composite_unique_is_refused_with_the_derived_name()
         .block_on(db.drop_column("T".to_string(), "a".to_string(), false, None))
         .expect_err("dropping a composite-UNIQUE column is refused");
     let msg = err.friendly_message();
-    assert!(msg.contains("unique_a_b"), "names the derived constraint; got: {msg}");
+    assert!(
+        msg.contains("unique_a_b"),
+        "names the derived constraint; got: {msg}"
+    );
     assert!(
         msg.contains("drop constraint unique_a_b"),
         "points at the actionable drop command; got: {msg}"
@@ -351,14 +355,24 @@ fn rename_column_with_a_column_level_check_is_refused() {
     make_t_with_column_checks(&db, &r);
     // `qty`'s own check `qty >= 0` references qty → refused.
     assert!(
-        r.block_on(db.rename_column("T".to_string(), "qty".to_string(), "amount".to_string(), None))
-            .is_err(),
+        r.block_on(db.rename_column(
+            "T".to_string(),
+            "qty".to_string(),
+            "amount".to_string(),
+            None
+        ))
+        .is_err(),
         "renaming a column with its own column-level CHECK is refused"
     );
     // `price` is referenced by `discount`'s check `discount < price`.
     assert!(
-        r.block_on(db.rename_column("T".to_string(), "price".to_string(), "cost".to_string(), None))
-            .is_err(),
+        r.block_on(db.rename_column(
+            "T".to_string(),
+            "price".to_string(),
+            "cost".to_string(),
+            None
+        ))
+        .is_err(),
         "renaming a column referenced by another column's CHECK is refused"
     );
     // `id` is referenced by no CHECK → rename succeeds.