MagicDNS short names fail on macOS: check /etc/resolver for stale third-party files

When MagicDNS resolves through dig but macOS apps cannot resolve a short name, inspect /etc/resolver/ for a stale search-domain file from another VPN or DNS tool. In the linked Tailscale report, an EasyTier file remained after EasyTier stopped and sent short-name queries to its resolver.

1. Compare dig @100.100.100.100 <short-name> with the app lookup, then inspect the files and nameservers under /etc/resolver/ and scutil --dns.
2. Move or disable only a file you have confirmed is redirecting the affected search domain. Use a destination that exists; do not move unrelated resolver files. Disable the other tool's search-domain integration if it recreates the file.
3. Flush the macOS DNS cache and recheck the same short name. Use a fully qualified name for domains owned by the other tool.

Source: Tailscale issue #20890 reports MagicDNS short names failing in macOS apps while direct queries to 100.100.100.100 worked; investigation identified a stale EasyTier /etc/resolver search-domain file directing queries to its resolver after EasyTier stopped. The inspection and conditional remediation above are scoped to that reported configuration; verify the actual file before changing it. Source: https://github.com/tailscale/tailscale/issues/20890