move tailscale to own configure step

migrations/1793101958.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Tailscale moved out of "configure core" into its own item, which records the
+# Core it joined in tailscale.conf rather than core.conf
+CORE_CONF="$HOME/.config/coredesktop/core.conf"
+TAILSCALE_CONF="$HOME/.config/coredesktop/tailscale.conf"
+
+[ -f "$CORE_CONF" ] || exit 0
+CORE_TAILSCALE="$(source "$CORE_CONF" && echo "$CORE_TAILSCALE")"
+if [ -n "$CORE_TAILSCALE" ] && [ ! -f "$TAILSCALE_CONF" ]; then
+  printf 'TAILSCALE_DOMAIN=%q\n' "$CORE_TAILSCALE" > "$TAILSCALE_CONF" || exit 1
+fi
+sed -i '/^CORE_TAILSCALE=/d' "$CORE_CONF"