feat(install): copy templates/downstream and patch install values

Make the downstream template the single source of truth for machine
flakes: nomarchy-install copies flake/system/home/theme-state and
patch-template.py only fills hostname, user, keyboard, detected
hardware, snapper, resume, and password. Install and flake-init users
now share the same commented opt-ins and starter home.packages.

Also: BACKLOG boreal-as-default proposal; installer audit notes;
HARDWARE.md from prior work if uncommitted.

templates/downstream/home.nix

@@ -2,17 +2,21 @@
 # Ghostty, theming engine, Stylix) comes from homeModules.nomarchy;
 # tune it via the nomarchy.* options, add your own packages and
 # programs below.
+#
+# Source of truth for install and flake-init: nomarchy-install copies this
+# file and only patches keyboard layout/variant.
 { pkgs, ... }:
 
 {
+  # Session keyboard — match services.xserver.xkb.* in system.nix (console
+  # + LUKS prompt follow xkb via the distro module). Installer patches these.
+  nomarchy.keyboard.layout = "us";
+  nomarchy.keyboard.variant = "";
+
   # ── Overrides (the desktop is on by default; tweak or opt out) ──────
   # nomarchy.terminal = "kitty";        # swap the default terminal
   # nomarchy.waybar.enable = false;     # bring your own bar
   # nomarchy.stylix.enable = false;     # opt out of GTK/Qt theming
-  # nomarchy.keyboard.layout = "de";    # session keyboard (set the matching
-  #                                     # services.xserver.xkb.layout in
-  #                                     # system.nix too; the console + LUKS
-  #                                     # prompt follow it automatically)
 
   # ── Opt-in features — uncomment and tweak to enable ─────────────────
   # nomarchy.nightlight = {             # scheduled blue-light filter (hyprsunset)