refactor(GFramework.SourceGenerators): 优化集合类型候选枚举逻辑

- 将嵌套循环重构为使用 SelectMany 扁平化集合类型参数
- 简化了候选元素类型的遍历逻辑
- 提高了代码可读性和性能
- 移除了不必要的 continue 语句
- 保持了原有的类型匹配功能不变

GFramework.SourceGenerators/Rule/ContextGetGenerator.cs

@@ -711,11 +711,11 @@ public sealed class ContextGetGenerator : IIncrementalGenerator
         if (readOnlyList is null || fieldType is not INamedTypeSymbol targetType)
             return false;
 
-        foreach (var candidateType in EnumerateCollectionTypeCandidates(targetType))
-        {
-            if (candidateType is not { TypeArguments: [var candidateElementType] })
-                continue;
+        var allTypeCandidates = EnumerateCollectionTypeCandidates(targetType)
+            .SelectMany(candidateType => candidateType.TypeArguments);
 
+        foreach (var candidateElementType in allTypeCandidates)
+        {
             var expectedSourceType = readOnlyList.Construct(candidateElementType);
             if (!expectedSourceType.IsAssignableTo(targetType))
                 continue;
@@ -724,10 +724,10 @@ public sealed class ContextGetGenerator : IIncrementalGenerator
             return true;
         }
 
+
         return false;
     }
 
-
     private static IEnumerable<INamedTypeSymbol> EnumerateCollectionTypeCandidates(INamedTypeSymbol typeSymbol)
     {
         yield return typeSymbol;