Enhanced GitHub App Installation Workflow

The GitHub app installation process has been significantly improved with better error handling and user guidance:

• Prerequisite Checks: The CLI now performs comprehensive checks before attempting GitHub app installation:
• Verifies GitHub CLI (gh) is installed
• Checks authentication status
• Validates required permissions (specifically the "workflow" scope)

• Detailed Error Messages: When issues are encountered, users now receive specific instructions:

  # If GitHub CLI is not installed:
  - macOS: brew install gh
  - Windows: winget install --id GitHub.cli
  - Linux: See installation instructions at https://github.com/cli/cli#installation
  
  # If not authenticated:
  - Run: gh auth login
  
  # If missing workflow permissions:
  - Run: gh auth refresh -h github.com -s workflow

• Workflow Update Dialog: When an existing Claude workflow is detected, users are presented with three options:

1. Update workflow file with latest version
2. Skip workflow update (configure secrets only)
3. Exit without making changes