chore(deps): migrate to Bevy 0.18

- BorderRadius is no longer a Component; moved into Node.border_radius
  field at all 15 spawn sites across 6 plugin files
- Events<T> renamed to Messages<T> in test code (12 files)
- KeyboardEvents SystemParam renamed to KeyboardMessages to match the
  MessageWriter rename done in the 0.17 hop
- WindowResolution::from((f32,f32)) removed; use (u32,u32) tuple in main.rs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/progress_plugin.rs

@@ -187,7 +187,7 @@ mod tests {
         });
         app.update();
 
-        let events = app.world().resource::<Events<LevelUpEvent>>();
+        let events = app.world().resource::<Messages<LevelUpEvent>>();
         let mut cursor = events.get_cursor();
         let fired: Vec<_> = cursor.read(events).copied().collect();
         assert_eq!(fired.len(), 1, "exactly one level-up");
@@ -204,7 +204,7 @@ mod tests {
         });
         app.update();
 
-        let events = app.world().resource::<Events<LevelUpEvent>>();
+        let events = app.world().resource::<Messages<LevelUpEvent>>();
         let mut cursor = events.get_cursor();
         assert!(cursor.read(events).next().is_none());
     }
@@ -219,7 +219,7 @@ mod tests {
         });
         app.update();
 
-        let events = app.world().resource::<Events<XpAwardedEvent>>();
+        let events = app.world().resource::<Messages<XpAwardedEvent>>();
         let mut cursor = events.get_cursor();
         let fired: Vec<_> = cursor.read(events).copied().collect();
         assert_eq!(fired.len(), 1);
@@ -238,7 +238,7 @@ mod tests {
         app.update();
 
         let total_xp = app.world().resource::<ProgressResource>().0.total_xp;
-        let events = app.world().resource::<Events<LevelUpEvent>>();
+        let events = app.world().resource::<Messages<LevelUpEvent>>();
         let mut cursor = events.get_cursor();
         let fired: Vec<_> = cursor.read(events).copied().collect();
         assert_eq!(fired.len(), 1);