refactor: consolidate app configurations and utility scripts

- Move 32+ app-specific scripts from features/apps/scripts/ to features/scripts/utils/ for centralized packaging.
- Create individual Nix modules for orphaned app configurations (btop, kitty, tmux, etc.) in features/apps/ using xdg.configFile.
- Fix broken paths in core/system/makima.nix and features/apps/vscode.nix.
- Update VSCode configuration to use the modern 'profiles.default.userSettings' API, resolving deprecation warnings.
- Merge duplicate 'nomarchy-launch-walker' scripts into a single robust utility.
- Remove stale root 'config/' directory.
- Update README.md and docs/creating-themes.md to reflect the new architecture and keybindings.
- Ensure all modules are correctly imported and verified via nix flake check.

features/scripts/utils/nomarchy-menu

@@ -348,8 +348,9 @@ show_main_menu() {
 
 go_to_menu() {
   case "${1,,}" in
-  *apps*) walker -p "Launch…" ;;
+  *apps*) nomarchy-launch-walker ;;
   *learn*) show_learn_menu ;;
+  *symbols*) nomarchy-launch-walker -m symbols ;;
   *trigger*) show_trigger_menu ;;
   *toggle*) show_toggle_menu ;;
   *share*) show_share_menu ;;