Fix intermittent mDNS resolution failures

Switch NetworkManager WiFi backend to iwd to resolve repeated
wpa_supplicant disconnects caused by nl80211 send_event_marker
incompatibility with iwlwifi. Each disconnect was triggering avahi
SIGHUP reloads, causing .local name resolution to fail for several
minutes at a time.

Also disable WiFi power save in TLP and enable IPv6 mDNS resolution
via NSS (nssmdns6) for hosts that only advertise IPv6 addresses.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hosts/modules/base.nix

@@ -110,6 +110,7 @@
   services.avahi = {
     enable = true;
     nssmdns4 = true; # Enables Avahi for name service lookups (e.g., in /etc/nsswitch.conf)
+    nssmdns6 = true; # Also resolve IPv6 mDNS addresses via NSS
     publish = {
       enable = true;
       addresses = true; # Publish your laptop's IP addresses

hosts/modules/desktop.nix

@@ -53,6 +53,7 @@
 
   # Enable networking
   networking.networkmanager.enable = true;
+  networking.networkmanager.wifi.backend = "iwd";
 
   # Enable CUPS to print documents.
   services.printing.enable = true;

hosts/modules/laptop.nix

@@ -22,6 +22,9 @@
       # START_CHARGE_THRESH_BAT0 = 40; # 40 and below it starts to charge
       STOP_CHARGE_THRESH_BAT0 = 81; # 80 and above it stops charging
 
+      WIFI_PWR_ON_AC = "off";
+      WIFI_PWR_ON_BAT = "off";
+
     };
   };
 }

readme.md

@@ -8,6 +8,16 @@ From within this directory:
 sudo nixos-rebuild switch --flake .
 ```
 
+# WiFi
+
+NetworkManager is enabled. Use the terminal UI to connect:
+
+```
+nmtui
+```
+
+Select "Activate a connection", pick your network, and enter the password.
+
 # Update and deploy
 
 From within this directory: