desktop: add sway/swayfx profile (dormant) with waybar, kanshi, cliphist

New profile_desktop_sway role gated by desktop_sessions_enabled, with
SwayFX effects, Waybar bar (1:1 with Polybar layout + pulseaudio),
swayidle + swaylock-effects for locking, swayosd for OSD, cliphist for
clipboard history and kanshi for multi-monitor profiles. Emptty gains
WAYLAND_SESSIONS_PATH + wayland-sessions dir. start-sway wrapper handles
session env (dbus-run-session, gpg-agent, turnstile env). Profile stays
dormant until a host opts in via desktop_sessions_enabled.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ansible/roles/packages_void/tasks/main.yml

@@ -61,6 +61,11 @@
             if 'i3' in (desktop_sessions_enabled | default([]))
             else []
           )
+        + (
+            (desktop_sway_packages | default([]))
+            if 'sway' in (desktop_sessions_enabled | default([]))
+            else []
+          )
         + (host_packages | default([]))
         )
         | unique