feat: add non-technical user onboarding

- setup.sh: interactive wizard for Docker check and auth configuration
- launch.sh: folder-picker launcher (macOS native dialog, zenity/kdialog on Linux, text fallback)
- launch.bat: Windows launcher using PowerShell folder browser + Git Bash
- claude.sh: friendlier error messages with actionable links; prompt setup.sh if .env missing
- hooks/pre-commit: add setup.sh and launch.sh to executable enforcement
- README: add Quick Start section aimed at non-technical users

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hooks/pre-commit

@@ -2,7 +2,7 @@
 # Ensure control scripts stay executable.
 set -euo pipefail
 
-SCRIPTS=(claude.sh build.sh hooks/pre-commit)
+SCRIPTS=(claude.sh build.sh setup.sh launch.sh hooks/pre-commit)
 
 for f in "${SCRIPTS[@]}"; do
     if [[ -f "$f" && ! -x "$f" ]]; then