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/main.rs

@@ -24,6 +24,7 @@ mod parse_error_pedagogy;
 mod project_lifecycle;
 mod replay_command;
 mod seed;
+mod show_list;
 mod sql_alter_table;
 mod sql_create_index;
 mod sql_create_table;
@@ -34,6 +35,5 @@ mod sql_drop_table;
 mod sql_insert;
 mod sql_select;
 mod sql_update;
-mod show_list;
 mod undo_snapshots;
 mod walking_skeleton;