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/toggle-dropdown.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+# toggle-dropdown.sh — toggle the dropdown foot terminal
+# Writes debug info to /tmp/sway-f12.log so we can diagnose from SSH
+
+LOG=/tmp/sway-f12.log
+echo "=== $(date) F12/Super+grave pressed ===" >> "$LOG"
+echo "WAYLAND_DISPLAY=$WAYLAND_DISPLAY" >> "$LOG"
+echo "USER=$USER XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR" >> "$LOG"
+
+# Find the sway socket
+SOCK=$(ls -t /run/user/$(id -u)/sway-ipc.*.sock 2>/dev/null | head -1)
+echo "SOCK=$SOCK" >> "$LOG"
+
+if [ -z "$SOCK" ]; then
+    echo "ERROR: no sway socket found" >> "$LOG"
+    notify-send -t 2000 "sway: no IPC socket" 2>>"$LOG" || true
+    exit 1
+fi
+
+# Check if a foot window is in the scratchpad (hidden)
+HIDDEN=$(SWAYSOCK=$SOCK swaymsg -t get_tree 2>>"$LOG" | python3 -c "
+import sys, json
+try:
+    tree = json.load(sys.stdin)
+    def find_app(node, app_id):
+        if node.get('app_id') == app_id and node.get('name', '').startswith('__i3'):
+            return node
+        for c in node.get('nodes', []) + node.get('floating_nodes', []):
+            r = find_app(c, app_id)
+            if r is not None:
+                return r
+        return None
+    dd = find_app(tree, 'foot')
+    print('hidden' if dd is not None else 'none')
+except Exception as e:
+    print(f'err:{e}')
+" 2>>"$LOG")
+
+echo "HIDDEN=$HIDDEN" >> "$LOG"
+
+if [ "$HIDDEN" = "hidden" ]; then
+    SWAYSOCK=$SOCK swaymsg '[app_id="foot"] scratchpad show' >>"$LOG" 2>&1
+    echo "toggled: scratchpad show" >> "$LOG"
+else
+    # Spawn a new foot. Pass through WAYLAND_DISPLAY explicitly.
+    if [ -n "$WAYLAND_DISPLAY" ]; then
+        WAYLAND_DISPLAY=$WAYLAND_DISPLAY foot >>"$LOG" 2>&1 &
+    else
+        # try to find wayland-1 socket
+        if [ -S "/run/user/$(id -u)/wayland-1" ]; then
+            WAYLAND_DISPLAY=wayland-1 foot >>"$LOG" 2>&1 &
+        else
+            foot >>"$LOG" 2>&1 &
+        fi
+    fi
+    echo "spawned foot" >> "$LOG"
+fi
+echo "=== done ===" >> "$LOG"