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/card_plugin/sync.rs

@@ -6,9 +6,9 @@ use super::*;
 use std::collections::{HashMap, HashSet};
 
 use bevy::color::Color;
-use solitaire_core::{Foundation, KlondikePile, Tableau};
 use solitaire_core::{Card, Rank, Suit};
 use solitaire_core::{DrawStockConfig, game_state::GameState};
+use solitaire_core::{Foundation, KlondikePile, Tableau};
 
 use crate::animation_plugin::{CARD_ANIM_Z_LIFT, CardAnim, EffectiveSlideDuration};
 use crate::card_animation::CardAnimation;
@@ -700,4 +700,3 @@ pub(super) fn update_card_entity(
         commands.entity(entity).insert(new_children_key);
     }
 }
-