Add secure clone-demo.sh script with comprehensive safety features

[Copilot]

This PR addresses critical security vulnerabilities in directory removal operations by implementing a secure clone-demo.sh script with comprehensive safety measures.

Key Security Improvements

Enhanced Portability

• Improved shebang declaration: Uses #!/usr/bin/env bash for better cross-platform compatibility
• Strict error handling: Implements set -euo pipefail to prevent script execution with errors

Critical Safety Validation

The script implements multi-layered validation before any directory removal operations:

# Protected system directories that cannot be removed
readonly PROTECTED_DIRS=(
    "/"
    "/bin"
    "/boot" 
    "/dev"
    "/etc"
    "/home"
    "/lib"
    "/usr"
    "/var"
    # ... and more
)

Comprehensive Protection Against Dangerous Directory Values

• System directory protection: Prevents removal of critical paths like /, /home, /usr, etc.
• Input validation: Rejects empty strings, whitespace-only paths, and dangerous patterns
• Path resolution: Uses readlink -f to resolve and validate absolute paths
• User confirmation: Requires explicit confirmation for all destructive operations
• Safe function design: safe_remove_directory() with multiple validation layers

Security Testing Results

The script successfully blocks dangerous operations:

• ❌ ./clone-demo.sh --force / → "Cannot remove protected directory"
• ❌ ./clone-demo.sh --force /home → "Cannot remove protected directory"
• ❌ ./clone-demo.sh --force "" → "Directory path cannot be empty"
• ✅ ./clone-demo.sh --help → Shows comprehensive usage and safety features

Additional Features

• Visual feedback: Color-coded output for different message types
• Comprehensive help: Detailed usage documentation with safety feature descriptions
• Flexible options: Support for custom repositories, force mode, and cleanup operations
• Error handling: Proper exit codes and descriptive error messages

The script prevents catastrophic system damage from potentially dangerous rm -rf commands while maintaining all existing functionality for legitimate demo setup operations.

Fixes #20.

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[joe10832]

@copilot