Flatten directory structure and update documentation

- Moved all files from mac_os/ subdirectory to repository root
- Updated README.adoc to reflect simplified architecture
- Updated QUICK_INSTALL.md with all current apps
- Added claude-cli to install.sh and bin/install_homebrew_formulas
- Repository now shows clean file structure without nested mac_os folder
- Documentation now accurately describes opinionated installer approach

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

bin/install_shell

@@ -0,0 +1,16 @@
+#! /usr/bin/env bash
+
+# Installs shell.
+
+set -o nounset
+set -o errexit
+set -o pipefail
+IFS=$'\n\t'
+
+SCRIPT_PATH="$MAC_OS_CONFIG_PATH/bin/install_shell"
+
+if [[ -x "$SCRIPT_PATH" ]]; then
+  "$SCRIPT_PATH"
+else
+  printf "%s\n" "WARNING: Shell script does not exist or is not executable."
+fi