feat: add ReadComponent and ReadSingleton methods

Introduce read-only access methods that return copies of components
to avoid unnecessary modification marking during iteration.

src/OECS/World.cs

@@ -251,14 +251,14 @@ public class World : IDisposable
             _changes.Pending.MarkComponentRemoved(entity, typeof(T));
     }
 
+    /// <summary>
     /// <summary>
     /// Returns a reference to the component of type <typeparamref name="T"/>
     /// for the given entity. Throws if the entity does not have the component.
     ///
-    /// During iteration (inside <see cref="ForEach"/> or a <c>Select</c> loop),
-    /// components accessed through this method are automatically marked as
-    /// modified when the iteration scope ends. Outside of iteration,
-    /// <see cref="MarkModified{T}"/> must be called explicitly.
+    /// During iteration, this access is auto-marked as modified since it
+    /// returns a mutable ref. Use <see cref="ReadComponent{T}"/> if you
+    /// only need to read the value.
     /// </summary>
     public ref T GetComponent<T>(Entity entity) where T : struct
     {
@@ -267,10 +267,21 @@ public class World : IDisposable
         return ref _components.Get<T>(entity);
     }
 
+    /// <summary>
+    /// Returns a copy of the component of type <typeparamref name="T"/>
+    /// for the given entity. Never auto-marks as modified — use this when
+    /// you only need to read the value.
+    /// </summary>
+    public T ReadComponent<T>(Entity entity) where T : struct
+    {
+        return _components.Get<T>(entity);
+    }
+
     /// <summary>
     /// Tries to get the component of type <typeparamref name="T"/> for the
     /// given entity. Returns true and copies the value to
     /// <paramref name="value"/> if the component exists; otherwise returns false.
+    /// Never auto-marks as modified.
     /// </summary>
     public bool TryGetComponent<T>(Entity entity, out T value) where T : struct
     {
@@ -352,7 +363,7 @@ public class World : IDisposable
 
     /// <summary>
     /// Returns a reference to the singleton component of type <typeparamref name="T"/>.
-    /// Throws if the singleton has not been set.
+    /// Throws if the singleton has not been set. Auto-marks as modified during iteration.
     /// </summary>
     public ref T GetSingleton<T>() where T : struct
     {
@@ -360,6 +371,16 @@ public class World : IDisposable
         return ref GetComponent<T>(SingletonEntity);
     }
 
+    /// <summary>
+    /// Returns a copy of the singleton component of type <typeparamref name="T"/>.
+    /// Never auto-marks as modified — use this when you only need to read the singleton.
+    /// </summary>
+    public T ReadSingleton<T>() where T : struct
+    {
+        EnsureSingleton();
+        return ReadComponent<T>(SingletonEntity);
+    }
+
     /// <summary>
     /// Returns true if a singleton component of type <typeparamref name="T"/> exists.
     /// </summary>