Add foreign static getter `isRaw` and setter `isRaw=(value)` to the Stdin class, backed by a new `isStdinRaw` boolean flag and `uv_tty_set_mode` calls. The getter returns the current raw mode state, while the setter initializes the stdin stream if needed and applies raw or normal mode only when stdin is a TTY. Also includes a test file verifying default false, reading bytes in normal mode, enabling raw mode, and reading subsequent bytes.
