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/hud_plugin/spawn.rs

@@ -2,7 +2,6 @@
 
 use super::*;
 
-
 #[cfg(not(target_arch = "wasm32"))]
 use crate::avatar_plugin::AvatarResource;
 
@@ -292,7 +291,9 @@ pub(super) fn spawn_avatar_child(
     const SIZE: f32 = 32.0;
     if let Some(handle) = avatar.and_then(|a| a.0.clone()) {
         // Logged-in with a downloaded avatar: keep the accent disc behind it.
-        commands.entity(parent).insert(BackgroundColor(ACCENT_PRIMARY));
+        commands
+            .entity(parent)
+            .insert(BackgroundColor(ACCENT_PRIMARY));
         // Image fills the circle container; border_radius clips it to a disc.
         commands.entity(parent).with_children(|b| {
             b.spawn((
@@ -549,4 +550,3 @@ pub(super) fn spawn_action_button<M: Component>(
         }
     });
 }
-