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/waybar/config

@@ -0,0 +1,102 @@
+{
+    "layer": "top",
+    "position": "top",
+    "height": 32,
+    "spacing": 0,
+    "modules-left": [
+        "sway/workspaces",
+        "sway/mode"
+    ],
+    "modules-center": [
+        "clock",
+        "custom/caffeine"
+    ],
+    "modules-right": [
+        "pulseaudio",
+        "battery",
+        "cpu",
+        "memory",
+        "tray",
+        "network"
+    ],
+    "sway/workspaces": {
+        "disable-scroll": true,
+        "format": "{name}",
+        "format-icons": {
+            "focused": "\u25cf",
+            "default": "\u25cb"
+        }
+    },
+    "clock": {
+        "format": "  {:%a %b %d  %H:%M}",
+        "tooltip-format": "<big>{:%Y %B}</big>\n<tt><small>{calendar}</small></tt>",
+        "format-alt": "  {:%Y-%m-%d}"
+    },
+    "pulseaudio": {
+        "format": "{icon}  {volume}%",
+        "format-muted": "\udb81\udd81  muted",
+        "format-icons": {
+            "default": [
+                "\udb81\udd7f",
+                "\udb81\udd80",
+                "\udb81\udd7e"
+            ]
+        },
+        "scroll-step": 5,
+        "on-click": "wpctl set-mute @DEFAULT_AUDIO_SINK@ toggle",
+        "on-click-right": "pavucontrol"
+    },
+    "battery": {
+        "states": {
+            "good": 80,
+            "warning": 30,
+            "critical": 15
+        },
+        "format": "{icon}  {capacity}%",
+        "format-charging": "\udb80\udc84  {capacity}%",
+        "format-plugged": "\udb80\udc84  {capacity}%",
+        "format-icons": [
+            "\udb80\udc8e",
+            "\udb80\udc7a",
+            "\udb80\udc7b",
+            "\udb80\udc7c",
+            "\udb80\udc7d",
+            "\udb80\udc7e",
+            "\udb80\udc7f",
+            "\udb80\udc80",
+            "\udb80\udc81",
+            "\udb80\udc82",
+            "\udb80\udc79"
+        ]
+    },
+    "cpu": {
+        "format": "\udb83\udee0  {usage}%",
+        "tooltip": true
+    },
+    "memory": {
+        "format": "\udb80\udf5b  {}%",
+        "tooltip-format": "{used:0.1f}G / {total:0.1f}G"
+    },
+    "network": {
+        "format-wifi": "\udb82\udd28  {essid}",
+        "format-ethernet": "\udb80\ude00  {ipaddr}",
+        "format-disconnected": "\udb82\udd2d  disconnected",
+        "format-linked": "\udb82\udd2a  {ifname}",
+        "tooltip-format": "{ifname} \u2014 {ipaddr}",
+        "on-click": "$HOME/.config/sway/wifi-menu.sh"
+    },
+    "custom/caffeine": {
+        "format": "{icon}",
+        "format-icons": {
+            "default": "\udb80\udd76",
+            "active": "\u2615"
+        },
+        "exec": "if [ -f /tmp/caffeine-inhibit ]; then echo '{\"alt\":\"active\",\"text\":\"caffeine\"}'; else echo '{\"alt\":\"default\",\"text\":\"caffeine\"}'; fi",
+        "exec-interval": 2,
+        "return-type": "json",
+        "on-click": "$HOME/.config/sway/caffeine.sh"
+    },
+    "tray": {
+        "spacing": 8
+    }
+}