Create update.sh script that fetches the latest claude-code version
and SHA256 hashes from Homebrew cask and automatically updates the
Nix package definition.
Features:
- Fetches version and all 4 platform SHA256 hashes from Homebrew
- Updates default.nix in-place using awk for reliable parsing
- Validates extracted data before updating
- Supports --dry-run mode to preview changes
- Supports --help flag for usage information
- Idempotent (safe to run multiple times)
Update README to document the automated update method as the
recommended approach, with manual update as a fallback option.
