feat: keymap/locale + form factor in installer; nm-applet visible by default

- Installer prompts for keyboard layout (with optional variant) and locale
  via curated short list + Other… fallback into the full localectl list;
  applies to the live session immediately (loadkeys + hyprctl) so the
  rest of the install types correctly. Generated system.nix emits
  console.keyMap, i18n.defaultLocale, and services.xserver.xkb.{layout,
  variant}.
- New nomarchy.{system,}.formFactor enum (laptop|desktop, default laptop).
  Installer auto-detects via /sys/class/power_supply/BAT* and lets the
  user flip the answer. Waybar drops the battery widget on desktop;
  battery-monitor service is gated on the same option.
- Lift waybar tray out of the collapsed group/tray-expander in the default
  theme so nm-applet's icon is visible without expanding the drawer.
- Live ISOs (TTY + graphical) get baseline mkDefault keyMap/locale so the
  installer's runtime override always wins.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

features/scripts/battery-monitor.nix

@@ -1,12 +1,12 @@
-{ pkgs, ... }:
+{ config, lib, pkgs, ... }:
 
-{
+lib.mkIf (config.nomarchy.formFactor == "laptop") {
   systemd.user.services.nomarchy-battery-monitor = {
     Unit = {
       Description = "Nomarchy Battery Monitor Check";
       After = [ "graphical-session.target" ];
-      # Skip on hosts with no battery (VMs, desktops) — otherwise the
-      # monitor script fails and degrades the user session.
+      # Belt-and-braces: even on a laptop generation, skip if the kernel
+      # hasn't surfaced a battery yet (e.g. early boot, removable battery).
       ConditionPathExistsGlob = "/sys/class/power_supply/BAT*";
     };