fix:1 添加 fat pointer 运行时探查 2 标记 ConsoleNode::write_at 入口 3 修改 VfsFile::write，在 write_at 调用前加 downcast_ref 直接调用,尝试 bypass vtable 分发 4 内核栈大小扩大至16KB,等待后续guard_page实现 5 - sys_exec: accept *const u8 / *const *const u8 (raw C-style pointers) - exec(): create null-terminated stack buffers for path and argv[0] - initproc: update exec call site to new signature (&[&str])