fix(coroutine): 修复协程扩展方法中的空引用和测试代码

- 为 RepeatEvery 方法的 action 参数添加可空引用支持
- 更新测试代码中集合断言的语法格式
- 移除测试方法中未使用的变量声明以简化代码
- 修复测试代码中 lambda 表达式的写法以避免不必要的变量赋值

GFramework.Core.Tests/coroutine/CoroutineComposeExtensionsTests.cs

@@ -117,7 +117,7 @@ public class CoroutineComposeExtensionsTests
             combined.Current.Update(0.016);
         }
 
-        Assert.That(executionOrder, Is.EqualTo(new[] { 1, 2, 3 }));
+        Assert.That(executionOrder, Is.EqualTo([1, 2, 3]));
     }
 
     /// <summary>

GFramework.Core.Tests/coroutine/CoroutineExtensionsTests.cs

@@ -109,8 +109,7 @@ public class CoroutineExtensionsTests
     [Test]
     public void ExecuteAfter_Should_Return_Valid_Coroutine()
     {
-        var called = false;
+        var coroutine = CoroutineExtensions.ExecuteAfter(1.0, () => _ = true);
-        var coroutine = CoroutineExtensions.ExecuteAfter(1.0, () => called = true);
 
         Assert.That(coroutine, Is.InstanceOf<IEnumerator<IYieldInstruction>>());
     }

GFramework.Core.Tests/coroutine/CoroutineHelperTests.cs

@@ -162,8 +162,7 @@ public class CoroutineHelperTests
     [Test]
     public void DelayedCall_Should_Return_IEnumerator()
     {
-        var called = false;
+        var coroutine = CoroutineHelper.DelayedCall(1.0, () => _ = true);
-        var coroutine = CoroutineHelper.DelayedCall(1.0, () => called = true);
 
         Assert.That(coroutine, Is.InstanceOf<IEnumerator<IYieldInstruction>>());
     }
@@ -300,8 +299,7 @@ public class CoroutineHelperTests
     [Test]
     public void DelayedCall_Should_Handle_Negative_Delay()
     {
-        var called = false;
+        var coroutine = CoroutineHelper.DelayedCall(-1.0, () => _ = true);
-        var coroutine = CoroutineHelper.DelayedCall(-1.0, () => called = true);
 
         Assert.That(coroutine, Is.Not.Null);
         Assert.DoesNotThrow(() => coroutine.MoveNext());

GFramework.Core/coroutine/extensions/CoroutineExtensions.cs

@@ -17,7 +17,7 @@ public static class CoroutineExtensions
     /// <returns>协程枚举器</returns>
     public static IEnumerator<IYieldInstruction> RepeatEvery(
         double interval,
-        Action action,
+        Action? action,
         int? count = null)
     {
         if (count is < 0) yield break;