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-browser

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# Launch the default browser as determined by xdg-settings.
+# Automatically converts --private into the correct flag for the given browser.
+
+default_browser=$(xdg-settings get default-web-browser)
+browser_exec=$(sed -n 's/^Exec=\([^ ]*\).*/\1/p' {~/.local,~/.nix-profile,/usr}/share/applications/$default_browser 2>/dev/null | head -1)
+
+if $browser_exec --help | grep -q MOZ_LOG; then
+  private_flag="--private-window"
+elif [[ $browser_exec =~ edge ]]; then
+  private_flag="--inprivate"
+else
+  private_flag="--incognito"
+fi
+
+exec setsid uwsm-app -- "$browser_exec" "${@/--private/$private_flag}"