build: package the desktop instead of the shell

The install list loses the dock, the window helper, the Chrome window
arbiter, the notification wrapper, the compositor and bar configs and the
GTK icon and stylesheet machinery, and gains a look and feel package, a
colour scheme, window rules, Kiosk restrictions and two supervised user
services. Dependencies follow: Plasma and SDDM in, sway, waybar, mako and
gtk-layer-shell out.

Co-Authored-By: Claude Opus 5 <[email protected]>

config/sddm/ekklesia-classroom.conf

@@ -0,0 +1,24 @@
+# The classroom logs itself in, and logs itself back in.
+#
+# The old session started from ~/.bash_profile on an autologin getty, which
+# has one bad property: when the session ends for any reason, the teacher is
+# looking at a shell prompt on a machine that is supposed to have no
+# terminal. A display manager ends that. Relogin means the room comes
+# straight back to the classroom instead of to anything else.
+#
+# SDDM is never seen. There is one user, no password, and no chooser.
+
+[Autologin]
+User=classroom
+Session=plasma
+Relogin=true
+
+[General]
+DisplayServer=wayland
+# No user switching, no second session.
+InputMethod=
+
+[Users]
+MaximumUid=1000
+MinimumUid=1000
+HideShells=/usr/sbin/nologin,/bin/false