style: cargo fmt under rustfmt 1.9 and gate formatting in CI

The repo was formatted under an older stable; rustfmt 1.9 (Rust 1.95)
wraps signatures and call sites differently, so every touched file was
picking up unrelated formatting hunks. One mechanical pass, and a
'cargo fmt --check' step in the test workflow (same pinned 1.95.0
toolchain) so drift can't accumulate again.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

solitaire_data/src/storage.rs

@@ -553,8 +553,8 @@ mod tests {
             "saved file must use schema version 5",
         );
 
-        let loaded = load_game_state_from(&path)
-            .expect("a valid in-progress game must load without error");
+        let loaded =
+            load_game_state_from(&path).expect("a valid in-progress game must load without error");
 
         // The forward instruction history round-trips, so the reconstructed board
         // re-serialises to byte-identical JSON.
@@ -569,7 +569,11 @@ mod tests {
 
         // Derived board reads match the live game (move count + recycle count are
         // both rebuilt from the replayed forward history).
-        assert_eq!(loaded.move_count(), gs.move_count(), "move_count round-trips");
+        assert_eq!(
+            loaded.move_count(),
+            gs.move_count(),
+            "move_count round-trips"
+        );
         assert_eq!(
             loaded.recycle_count(),
             gs.recycle_count(),