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/typing_surface/explain.rs

@@ -66,10 +66,7 @@ fn complete_explain_show_data_parses_as_explain() {
 #[test]
 fn complete_explain_show_data_with_where_and_limit_parses() {
     let schema = schema_serial_pk();
-    let a = assess_at_end(
-        "explain show data Customers where id = 1 limit 5",
-        &schema,
-    );
+    let a = assess_at_end("explain show data Customers where id = 1 limit 5", &schema);
     assert!(matches!(a.state, InputState::Valid));
     assert_eq!(a.parse_result.as_deref(), Ok("Explain"));
     crate::snap!("complete_explain_show_data_where_limit", a);
@@ -95,10 +92,7 @@ fn after_explain_update_table_expects_set() {
 #[test]
 fn complete_explain_update_parses_as_explain() {
     let schema = schema_serial_pk();
-    let a = assess_at_end(
-        "explain update Customers set Name='Bo' where id=1",
-        &schema,
-    );
+    let a = assess_at_end("explain update Customers set Name='Bo' where id=1", &schema);
     assert!(matches!(a.state, InputState::Valid));
     assert_eq!(a.parse_result.as_deref(), Ok("Explain"));
     crate::snap!("complete_explain_update", a);