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/auto_complete_plugin.rs

@@ -174,9 +174,9 @@ mod tests {
     use super::*;
     use crate::game_plugin::GamePlugin;
     use crate::table_plugin::TablePlugin;
-    use solitaire_core::{Foundation, KlondikePile, Tableau};
     use solitaire_core::{Deck, Rank, Suit};
     use solitaire_core::{DrawStockConfig, game_state::GameState};
+    use solitaire_core::{Foundation, KlondikePile, Tableau};
 
     fn headless_app() -> App {
         let mut app = App::new();
@@ -214,7 +214,11 @@ mod tests {
         }
         g.set_test_tableau_cards(
             Tableau::Tableau1,
-            vec![solitaire_core::Card::new(Deck::Deck1, Suit::Clubs, Rank::Ace)],
+            vec![solitaire_core::Card::new(
+                Deck::Deck1,
+                Suit::Clubs,
+                Rank::Ace,
+            )],
         );
         g.set_test_auto_completable(true);
         let expected = (