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>

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,8 @@
+## Overview
+<!-- Required. Describe, briefly, why this is necessary and what the overarching architecture is. -->
+
+## Screenshots/Screencasts
+<!-- Optional. Provide supporting screen shots/casts. -->
+
+## Details
+<!-- Optional. As bullet points, list related issue(s); major highlights; team callouts; and/or other information that is helpful. -->