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-launch-editor

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+# Launch the default editor as determined by $EDITOR (set via ~/.config/uwsm/default) (or nvim if missing).
+# Starts suitable editors in a terminal window and otherwise as a regular application.
+
+nomarchy-cmd-present "$EDITOR" || EDITOR=nvim
+
+case "$EDITOR" in
+nvim | vim | nano | micro | hx | helix | fresh)
+  exec nomarchy-launch-tui "$EDITOR" "$@"
+  ;;
+*)
+  exec setsid uwsm-app -- "$EDITOR" "$@"
+  ;;
+esac