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>

dotfiles/desktop/.config/sway/scripts/powermenu.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+
+choice="$(printf "⏻  Shutdown\n  Reboot\n  Logout\n  Lock\n⏾  Suspend" \
+| rofi -dmenu \
+-i \
+-p "Power" \
+-theme ~/.config/rofi/config.rasi \
+-theme-str 'window { width: 20%; location: center; anchor: center; } listview { columns: 1; spacing: 6px; }')"
+
+[ -z "$choice" ] && exit 0
+
+case "$choice" in
+    *Lock)
+        ~/.config/sway/scripts/lockscreen
+        ;;
+    *Logout)
+        swaymsg exit
+        ;;
+    *Suspend)
+        ~/.config/sway/scripts/lockscreen
+        loginctl suspend
+        ;;
+    *Reboot)
+        loginctl reboot
+        ;;
+    *Shutdown)
+        loginctl poweroff
+        ;;
+esac