More tests and WIP vibe work

Chrono/Shared/Services/CardPreviewService.cs

@@ -0,0 +1,31 @@
+using Microsoft.AspNetCore.Components;
+using Model;
+
+namespace Shared.Services;
+
+public class CardPreviewService
+{
+    public CardData? HoveredCard { get; private set; }
+    public double X { get; private set; }
+    public double Y { get; private set; }
+    public bool IsVisible { get; private set; }
+
+    public event Action? OnChange;
+
+    public void Show(CardData card, double x, double y)
+    {
+        HoveredCard = card;
+        X = x;
+        Y = y;
+        IsVisible = true;
+        NotifyStateChanged();
+    }
+
+    public void Hide()
+    {
+        IsVisible = false;
+        NotifyStateChanged();
+    }
+
+    private void NotifyStateChanged() => OnChange?.Invoke();
+}