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/iteration4a_rebuild_command.rs

@@ -113,7 +113,10 @@ fn modal_swallows_unrelated_keys() {
     // field while the modal is up.
     app.update(key(KeyCode::Char('x')));
     assert!(app.input.is_empty(), "modal should swallow key input");
-    assert!(app.modal.is_some(), "modal still active after unrelated key");
+    assert!(
+        app.modal.is_some(),
+        "modal still active after unrelated key"
+    );
 }
 
 #[test]
@@ -122,11 +125,8 @@ fn rebuild_against_populated_db_wipes_and_reloads() {
     let project_path = {
         let project = project::open_or_create(None, Some(data.path())).unwrap();
         let path = project.path().to_path_buf();
-        let db = Database::open_with_persistence(
-            project.db_path(),
-            Persistence::new(path.clone()),
-        )
-        .unwrap();
+        let db = Database::open_with_persistence(project.db_path(), Persistence::new(path.clone()))
+            .unwrap();
         rt().block_on(async {
             db.create_table(
                 "Customers".to_string(),
@@ -156,7 +156,9 @@ fn rebuild_against_populated_db_wipes_and_reloads() {
     // Hand-edit the CSV to introduce a different row content.
     // Rebuild should pick up the edited content.
     let csv_path = project_path.join("data").join("Customers.csv");
-    let edited = fs::read_to_string(&csv_path).unwrap().replace("Alice", "Edna");
+    let edited = fs::read_to_string(&csv_path)
+        .unwrap()
+        .replace("Alice", "Edna");
     fs::write(&csv_path, edited).unwrap();
 
     // Reopen with persistence (the .db still exists but has