refactor: major architectural restructure for theme-centric organization

Theme System:
- Move all theme app configs to apps/ subdirectory (20 themes)
- Add theme-loader.nix for dynamic theme config deployment
- Simplify stylix.nix to focus on base theming only

Override System:
- Add overrides.nix for file-based config overrides
- Add behavior-configs.nix for non-visual configuration
- Split hypr/nomarchy.conf into behavior vs visual sections

Module Improvements:
- Add lib.mkDefault to all customizable settings
- Add modules/lib/ with shared utilities and state schema
- Update all home and system modules for downstream overridability

Installer:
- New minimal TTY installer (installer/install.sh)
- Golden path: BTRFS + LUKS2 (disko-golden.nix)
- New installer-iso.nix for TTY-only installation
- Keep graphical installer as installerIsoGraphical option

Cleanup:
- Remove obsolete install.sh, disko-ext4.nix, install-nomarchy.sh
- Update live-iso.nix references
- Add .claude/ to .gitignore for local IDE settings

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

modules/home/walker.nix

@@ -1,10 +1,10 @@
-{ config, pkgs, ... }:
+{ config, pkgs, lib, ... }:
 
 {
   programs.walker = {
-    enable = true;
-    runAsService = true;
-    config = {
+    enable = lib.mkDefault true;
+    runAsService = lib.mkDefault true;
+    config = lib.mkDefault {
       theme = "nomarchy";
       ui = {
         anchors = {
@@ -14,7 +14,7 @@
       selection_wrap = true;
       hide_action_hints = true;
       placeholders = {
-        "default" = { input = " Search..."; list = "No Results"; };
+        "default" = { input = " Search..."; list = "No Results"; };
       };
       keybinds = {
         quick_activate = [];
@@ -38,7 +38,7 @@
         ];
       };
     };
-    themes."nomarchy" = {
+    themes."nomarchy" = lib.mkDefault {
       style = ''
         * {
           color: #${config.colorScheme.palette.base05};