Add comprehensive guidance for writing reliable helper scripts that avoid
infinite retry loops when VPN or network-dependent credential helpers fail.
Includes:
- TTL configuration documentation (CLAUDE_CODE_API_KEY_HELPER_TTL_MS)
- Timeout best practices for network operations
- VPN-aware connectivity checks
- Local token caching patterns
- Troubleshooting guide for common issues
Addresses feedback from New Relic about apiKeyHelper retry loop behavior.