refactor(tpv): Gen 目录按前缀分组迁移子目录 + REnum.kind() 编译期转 __tag

- Gen/*.vp 按前缀分组迁入 Call/Class/Expr/Func/Stmt/Type 子目录，import 同步更新（BuildPipeline/Generator/StructGenMixin 等）

- CallGenDispatch: REnum.kind() 前置拦截 → bitcast i32* + load（读 __tag），杜绝方法查找兜底误绑 AST.kind（this 偏移语义错误）

- 留根：Assign/Async/Base/Imports/Match/Struct/Translator/Var 单文件前缀 + GenApi/GenTypes/Generator/__init__

App/lib/core/Gen/AsyncGenMixin.vp

@@ -13,7 +13,7 @@ import lib.core.VLogger as VLogger
 import lib.core.Handles.HandlesTranslator as HT
 import lib.core.Handles.HandlesExpr as HandlesExpr
 import lib.core.Handles.HandlesExprCall as HandlesExprCall
-import lib.core.Gen.CallGenBase as CallGenBase
+import lib.core.Gen.Call.CallGenBase as CallGenBase
 
 
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