refactor: rename iteration to batching and expand scope

Rename `BeginIteration`/`EndIteration` to `BeginBatching`/`EndBatching`
to reflect that the mechanism now covers both entity iteration and
system execution.

- Update `ISystem` and `ITickedSystem` to use `RunImpl` for logic.
- Add `SystemExtensions.Run` to wrap system execution in a batching
  scope.
- Update `SystemGroup` to wrap system execution in a batching scope.
- Update `WorldQueryExtensions` to use the new batching terminology.

OECS/ISystem.cs

@@ -2,12 +2,44 @@ namespace OECS;
 
 /// <summary>
 /// A system that runs on every tick.
-/// Systems receive the world in their <see cref="Run"/> method.
+/// Implement <see cref="RunImpl"/> with the system logic.
+/// Call <see cref="ISystem.Run"/> to execute with batching.
 /// </summary>
 public interface ISystem
 {
     /// <summary>
-    /// Executes the system logic for this tick.
+    /// Implement this with the system's logic for this tick.
+    /// The caller (e.g., <see cref="ISystem.Run"/>) wraps this
+    /// in a batching scope so mutations and component accesses
+    /// are automatically tracked.
     /// </summary>
-    void Run(World world);
+    void RunImpl(World world);
+}
+
+/// <summary>
+/// Extension methods for running systems with proper batching.
+/// </summary>
+public static class SystemExtensions
+{
+    /// <summary>
+    /// Runs a system with a batching scope. Structural mutations are
+    /// buffered, and <see cref="World.GetComponent{T}"/> calls are
+    /// auto-tracked for modification until the system returns.
+    /// </summary>
+    public static void Run(this ISystem system, World world)
+    {
+        world.BeginBatching();
+        system.RunImpl(world);
+        world.EndBatching();
+    }
+
+    /// <summary>
+    /// Runs a ticked system with a batching scope.
+    /// </summary>
+    public static void Run(this ITickedSystem system, World world, Tick tick)
+    {
+        world.BeginBatching();
+        system.RunImpl(world, tick);
+        world.EndBatching();
+    }
 }

OECS/ITickedSystem.cs

@@ -7,7 +7,7 @@ namespace OECS;
 public interface ITickedSystem : ISystem
 {
     /// <summary>
-    /// Executes the system logic with tick information.
+    /// Implement this with the system's ticked logic.
     /// </summary>
-    void Run(World world, Tick tick);
+    void RunImpl(World world, Tick tick);
 }

OECS/SystemGroup.cs

@@ -62,6 +62,7 @@ public class SystemGroup
         // sees their effects.
         _world.ExecuteCommands();
 
+        _world.BeginBatching();
         foreach (var system in _systems)
         {
             if (system is ITickedSystem ticked)
@@ -77,10 +78,15 @@ public class SystemGroup
             // see the effects of commands enqueued by prior systems.
             _world.ExecuteCommands();
 
+            // Flush pending mutations so subsequent systems see
+            // entity/component changes from commands and previous systems.
+            _world.FlushPendingMutations();
+
             // Post changes after each system so subscribers see
             // incremental updates.
             _world.PostChanges();
         }
+        _world.EndBatching();
 
         // Drain any remaining commands (e.g., those enqueued outside systems).
         _world.ExecuteCommands();

OECS/World.cs

@@ -19,10 +19,11 @@ public class World : IDisposable
     private readonly Dictionary<Type, Entity> _singletonEntities = new();
     private bool _disposed;
 
-    // Deferred structural mutation support: when iterating entities,
+    // Deferred structural mutation support: when inside a batching scope
-    // AddComponent, RemoveComponent, and DestroyEntity are buffered and
+    // (e.g., a foreach iteration or a system run), AddComponent,
-    // applied after the iteration completes.
+    // RemoveComponent, and DestroyEntity are buffered and applied when
-    private int _iterationDepth;
+    // the outermost scope ends.
+    private int _batchingDepth;
     private readonly List<PendingMutation> _pendingMutations = new();
 
     private enum PendingMutationKind { AddComponent, RemoveComponent, DestroyEntity }
@@ -35,10 +36,10 @@ public class World : IDisposable
         public Type ComponentType;
     }
 
-    // Auto-dirty-marking: during iteration, component accesses via
+    // Auto-dirty-marking: during a batching scope, component accesses via
-    // GetComponent<T> are tracked. When the iteration scope ends,
+    // GetComponent<T> are tracked. When the scope ends, all accessed
-    // all accessed components are automatically marked as modified.
+    // components are automatically marked as modified.
-    // Outside of iteration, MarkModified<T> must be called explicitly.
+    // Outside of a batching scope, MarkModified<T> must be called explicitly.
     private readonly HashSet<(Entity Entity, Type ComponentType)> _accessedComponents = new();
     private readonly HashSet<(Entity Entity, Type ComponentType)> _markedModified = new();
 
@@ -86,7 +87,7 @@ public class World : IDisposable
     /// </summary>
     public void DestroyEntity(Entity entity)
     {
-        if (_iterationDepth > 0)
+        if (_batchingDepth > 0)
         {
             _pendingMutations.Add(new PendingMutation
             {
@@ -157,7 +158,7 @@ public class World : IDisposable
     /// </summary>
     public void AddComponent<T>(Entity entity, T component) where T : struct
     {
-        if (_iterationDepth > 0)
+        if (_batchingDepth > 0)
         {
             _pendingMutations.Add(new PendingMutation
             {
@@ -226,7 +227,7 @@ public class World : IDisposable
     /// </summary>
     public void RemoveComponent<T>(Entity entity) where T : struct
     {
-        if (_iterationDepth > 0)
+        if (_batchingDepth > 0)
         {
             _pendingMutations.Add(new PendingMutation
             {
@@ -269,7 +270,7 @@ public class World : IDisposable
     /// </summary>
     public ref T GetComponent<T>(Entity entity) where T : struct
     {
-        if (_iterationDepth > 0)
+        if (_batchingDepth > 0)
             _accessedComponents.Add((entity, typeof(T)));
         return ref _components.Get<T>(entity);
     }
@@ -465,23 +466,25 @@ public class World : IDisposable
     // ── Iteration Lifecycle ──────────────────────────────────────────
 
     /// <summary>
-    /// Begins an iteration scope. Structural mutations are buffered
+    /// Begins a batching scope. Structural mutations (AddComponent,
-    /// until <see cref="EndIteration"/> is called.
+    /// RemoveComponent, DestroyEntity) are buffered until the outermost
+    /// <see cref="EndBatching"/> call. Component accesses via
+    /// <see cref="GetComponent{T}"/> are auto-tracked for modification.
     /// </summary>
-    internal void BeginIteration()
+    internal void BeginBatching()
     {
-        _iterationDepth++;
+        _batchingDepth++;
     }
 
     /// <summary>
-    /// Ends an iteration scope. When the outermost scope ends, all
+    /// Ends a batching scope. When the outermost scope ends, all
     /// buffered structural mutations are applied and auto-tracked
     /// component modifications are posted.
     /// </summary>
-    internal void EndIteration()
+    internal void EndBatching()
     {
-        _iterationDepth--;
+        _batchingDepth--;
-        if (_iterationDepth == 0)
+        if (_batchingDepth == 0)
         {
             // Auto-mark all components accessed via GetComponent<T>
             // during the iteration as modified.
@@ -499,7 +502,7 @@ public class World : IDisposable
         }
     }
 
-    private void FlushPendingMutations()
+    internal void FlushPendingMutations()
     {
         if (_pendingMutations.Count == 0)
             return;

OECS/WorldQueryExtensions.cs

@@ -117,7 +117,7 @@ public ref struct Select1<T1> where T1 : struct
         _set = _store.GetSet(typeof(T1)) as SparseSet<T1>;
         _count = _set?.Count ?? 0;
         _index = -1;
-        _world.BeginIteration();
+        _world.BeginBatching();
     }
 
     /// <summary>The current entity handle.</summary>
@@ -147,7 +147,7 @@ public ref struct Select1<T1> where T1 : struct
 
     public void Dispose()
     {
-        _world.EndIteration();
+        _world.EndBatching();
     }
 
     private bool PassesWithout()
@@ -188,7 +188,7 @@ public ref struct Select2<T1, T2> where T1 : struct where T2 : struct
         _swapped = c2 < c1;
         _count = _swapped ? c2 : c1;
         _index = -1;
-        _world.BeginIteration();
+        _world.BeginBatching();
     }
 
     public Entity Entity { get; private set; }
@@ -221,7 +221,7 @@ public ref struct Select2<T1, T2> where T1 : struct where T2 : struct
 
     public Select2<T1, T2> GetEnumerator() => this;
 
-    public void Dispose() => _world.EndIteration();
+    public void Dispose() => _world.EndBatching();
 
     private bool PassesWithout()
     {
@@ -268,7 +268,7 @@ public ref struct Select3<T1, T2, T3>
         else { _driver = 0; _count = c1; }
 
         _index = -1;
-        _world.BeginIteration();
+        _world.BeginBatching();
     }
 
     public Entity Entity { get; private set; }
@@ -310,7 +310,7 @@ public ref struct Select3<T1, T2, T3>
 
     public Select3<T1, T2, T3> GetEnumerator() => this;
 
-    public void Dispose() => _world.EndIteration();
+    public void Dispose() => _world.EndBatching();
 
     private bool PassesWithout()
     {
@@ -360,7 +360,7 @@ public ref struct Select4<T1, T2, T3, T4>
         _count = min;
 
         _index = -1;
-        _world.BeginIteration();
+        _world.BeginBatching();
     }
 
     public Entity Entity { get; private set; }
@@ -412,7 +412,7 @@ public ref struct Select4<T1, T2, T3, T4>
 
     public Select4<T1, T2, T3, T4> GetEnumerator() => this;
 
-    public void Dispose() => _world.EndIteration();
+    public void Dispose() => _world.EndBatching();
 
     private bool PassesWithout()
     {
@@ -466,7 +466,7 @@ public ref struct Select5<T1, T2, T3, T4, T5>
         _count = min;
 
         _index = -1;
-        _world.BeginIteration();
+        _world.BeginBatching();
     }
 
     public Entity Entity { get; private set; }
@@ -530,7 +530,7 @@ public ref struct Select5<T1, T2, T3, T4, T5>
 
     public Select5<T1, T2, T3, T4, T5> GetEnumerator() => this;
 
-    public void Dispose() => _world.EndIteration();
+    public void Dispose() => _world.EndBatching();
 
     private bool PassesWithout()
     {
@@ -588,7 +588,7 @@ public ref struct Select6<T1, T2, T3, T4, T5, T6>
         _count = min;
 
         _index = -1;
-        _world.BeginIteration();
+        _world.BeginBatching();
     }
 
     public Entity Entity { get; private set; }
@@ -666,7 +666,7 @@ public ref struct Select6<T1, T2, T3, T4, T5, T6>
 
     public Select6<T1, T2, T3, T4, T5, T6> GetEnumerator() => this;
 
-    public void Dispose() => _world.EndIteration();
+    public void Dispose() => _world.EndBatching();
 
     private bool PassesWithout()
     {