Add sway/wofi/foot Wayland desktop stack with per-host toggle

New opt-in feature for x86_64 desktops: sway + wofi + foot + swaybg +
swaylock + swayidle + grim + slurp + waybar + wl-clipboard. mako on
arch, dunst on debian (mako isn't packaged for debian).

Files:
- .chezmoi.yaml.tmpl: added data.sway flag (true on miche/byte/kaiser,
  false on Pis). Override per host with ~/.config/chezmoi/features/sway
  or ~/.config/chezmoi/features/no-sway marker files.
- run_once_40-install-sway.sh.tmpl: installs packages if .sway=true,
  exits 0 otherwise. Sets up the marker file.
- dot_config/{sway,foot,wofi,waybar,mako}/: existing configs from miche.

Per-host toggle workflow:
  # On any box, enable sway:
  touch ~/.config/chezmoi/features/sway
  chezmoi apply

  # On a sway-enabled box, disable it:
  touch ~/.config/chezmoi/features/no-sway
  rm ~/.config/chezmoi/features/sway
  chezmoi apply

Currently sway packages are already installed on miche (existed before
this commit). Byte will get them via the new run_once_40 script.
Pis (rye, crouton) are unaffected — install script early-returns.

dot_config/sway/caffeine.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+# caffeine.sh — toggle caffeine mode by killing/restarting swayidle
+# When ON: kill swayidle (no idle lock/screen-off)
+# When OFF: restart swayidle with normal timeouts
+
+WALLPAPER="$HOME/.local/share/wallpapers/teach-invaders-gruvbox.png"
+FLAG="/tmp/caffeine-inhibit"
+
+if [ -f "$FLAG" ]; then
+    # Turn OFF caffeine — restart swayidle
+    rm -f "$FLAG"
+    killall swayidle 2>/dev/null
+    swayidle -w \
+        timeout 300 "swaylock -f -i $WALLPAPER" \
+        timeout 600 'swaymsg "output * power off"' \
+        resume 'swaymsg "output * power on"' \
+        before-sleep "swaylock -f -i $WALLPAPER" &
+    notify-send -t 2000 "☕ Caffeine OFF" "Idle sleep enabled" 2>/dev/null
+else
+    # Turn ON caffeine — kill swayidle
+    touch "$FLAG"
+    killall swayidle 2>/dev/null
+    notify-send -t 2000 "☕ Caffeine ON" "Idle sleep disabled" 2>/dev/null
+fi