fix(narrow): StmtGenMixin exc_code 显式 int(cst_r.int_val)

ast.Constant.int_val 为 int64，exc_code 为 int（并传入 const_int32），改用显式 int(...)

App/lib/core/Gen/Stmt/StmtGenMixin.vp

@@ -438,7 +438,7 @@ novirtual class StmtGenMixin(StmtGenDeclMixin.StmtGenDeclMixin):
         exc_msg: mlirlite.Value* = None
         if ek == ast.ASTKind.Constant:
             cst_r: ast.Constant* = ast.Constant*(rn.exc)
-            if cst_r is not None and cst_r.const_kind == ast.CONST_INT: exc_code = cst_r.int_val
+            if cst_r is not None and cst_r.const_kind == ast.CONST_INT: exc_code = int(cst_r.int_val)
         elif ek == ast.ASTKind.Name:
             enm2: ast.Name* = ast.Name*(rn.exc)
             if enm2.id is not None: