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_engine/src/pause_plugin.rs

@@ -969,7 +969,10 @@ mod tests {
         let mut app = App::new();
         app.add_plugins(MinimalPlugins).add_plugins(PausePlugin);
         app.init_resource::<ButtonInput<KeyCode>>();
-        app.insert_resource(GameStateResource(GameState::new(1, DrawStockConfig::DrawOne)));
+        app.insert_resource(GameStateResource(GameState::new(
+            1,
+            DrawStockConfig::DrawOne,
+        )));
         app.update();
         app
     }