Documents the non-obvious failure mode where /etc/hosts generator scripts
using `tailscale status --json | jq '.HostName'` get poisoned by iOS
peers, which always report HostName as the literal string "localhost"
because iOS doesn't expose the device name to apps.
Includes the buggy and fixed jq filter (use .DNSName first label
instead), a real-world Postfix outage example, and a verification
checklist. Linked from troubleshooting index and SUMMARY.
Discovered while diagnosing a 24h Postfix outage on majordiscord.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
