Pseudo-terminals, and what tmux and htop needed around them

- /dev/ptmx and /dev/pts/N: Unix98 pairs with a full line discipline,
  window sizes, job control and hangup (kernel/dev/pty.c).
- The console speaks scroll regions, insert/delete line, SU/SD, RI/IND/NEL,
  DECSC/DECRC; swallows charset designations and private CSI sequences;
  and LF only returns the carriage under ONLCR.
- setsid() drops the controlling terminal, so a pane's pty becomes its ctty.
- pipe2() honours O_NONBLOCK and O_CLOEXEC (libevent's signal pipe).
- File modes are stored and enforced: chmod, fchmod(at), umask, creation
  modes; /tmp is 1777.
- /proc/stat has real user/system/idle; /proc/<pid>/task; kthread flag.
- SO_PEERCRED, IOV_MAX 1024.
- /proc/strace: name a program and its syscalls go to the kernel log.
- World gains htop, btop, tmux, mc, ncdu, fastfetch, games, X toys, NetSurf.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

ports/alpine/world

@@ -26,3 +26,24 @@ xinit
 windowmaker
 xterm
 font-dejavu
+# Stress: terminal programs that draw, multiplex and poll. htop and btop read
+# /proc hard; tmux wants ptys, sockets and signals; mc does everything at once.
+htop
+btop
+tmux
+mc
+ncdu
+fastfetch
+# Games. In the terminal: nethack, the BSD set, and two toys. On X: lbreakout2
+# (SDL 1.2) and the classic X clients.
+nethack
+bsd-games
+cmatrix
+sl
+lbreakout2
+xeyes
+xclock
+xcalc
+# A browser: NetSurf, on GTK 3 -- glib's threads, cairo, pango, TLS. The step
+# before WebKit (epiphany), which is `apk add` away.
+netsurf