Leave Wi-Fi to NetworkManager when archinstall turned on iwd as well

archinstall's "Copy ISO network configuration", which a user who connected
with iwctl may pick, turns on iwd and systemd-networkd. CoreDesktop then
turns on NetworkManager too, and after a restart two services fight over
the Wi-Fi card. system/wifi.sh disables iwd and systemd-networkd, without
stopping them, when NetworkManager is enabled and isn't set to use iwd
itself. install.sh runs it, and a migration runs it on existing machines.
The README tells users to choose NetworkManager in archinstall.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

system/wifi.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+#
+# Purpose : Leave Wi-Fi to NetworkManager alone. archinstall's "copy ISO network
+#           configuration" turns on iwd and systemd-networkd, so a machine set
+#           up with iwctl from the Arch ISO can have them running alongside
+#           NetworkManager, which CoreDesktop turns on. Then two services fight
+#           over the Wi-Fi card: connections drop, or Wi-Fi is missing from
+#           GNOME.
+#
+# This disables iwd and systemd-networkd without stopping them, so the network
+# stays up until the next boot; after it, NetworkManager runs Wi-Fi and wired
+# connections. iwd's saved Wi-Fi passwords don't carry over: choose the network
+# once in GNOME's top-right menu.
+#
+# Changes nothing when NetworkManager isn't enabled, or when it is set up to
+# use iwd itself (wifi.backend=iwd in /etc/NetworkManager/conf.d/).
+
+systemctl is-enabled -q NetworkManager.service 2> /dev/null || exit 0
+systemctl is-enabled -q iwd.service 2> /dev/null || exit 0
+
+# Unset settings print commented out, so this matches only one someone set
+if NetworkManager --print-config 2> /dev/null \
+    | grep -qE '^[[:space:]]*wifi\.backend[[:space:]]*=[[:space:]]*iwd[[:space:]]*$'; then
+  exit 0
+fi
+
+echo "Turning off iwd, so that NetworkManager runs Wi-Fi from the next restart..."
+sudo systemctl disable iwd.service || exit 1
+
+# archinstall turns systemd-networkd on with iwd. Its wait-online would hold up
+# boot with nothing for it to wait for.
+if systemctl is-enabled -q systemd-networkd.service 2> /dev/null; then
+  echo "Turning off systemd-networkd, so that NetworkManager runs the network..."
+  sudo systemctl disable systemd-networkd.service systemd-networkd.socket \
+    systemd-networkd-wait-online.service || exit 1
+fi
+
+echo "After you restart, choose your Wi-Fi network in GNOME's top-right menu"
+echo "and enter its password once. The network stays up until then."