getty: show the text cursor at the login prompt (ESC[?25h)

The framebuffer login prompt had no visible caret (unlike a Linux VT): boot
output / the \x1Bc reset path can leave DECTCEM off. Emit ESC[?25h (show cursor)
alongside the pre-login clear so the prompt shows a cursor. (If fbcond does not
render a cursor glyph at all, that is a separate fbcond gap.)

src/bin/getty.rs

@@ -244,6 +244,10 @@ fn daemon(tty: &mut File, clear: bool, contain: bool, stderr: &mut Stderr) {
         if clear {
             let _ = redox::write(tty_fd as usize, b"\x1Bc");
         }
+        // Make the text cursor visible for the login prompt. Boot output (and the
+        // \x1Bc reset paths) can leave DECTCEM off, so the prompt shows with no
+        // caret — unlike a Linux VT. ESC[?25h = show cursor (DECTCEM).
+        let _ = redox::write(tty_fd as usize, b"\x1B[?25h");
         let _ = redox::fsync(tty_fd as usize);
 
         let slave_stdin = redox::open(&pty, flag::O_CLOEXEC | flag::O_RDONLY, 0)