Don't panic on broken pipe (e.g. npmctl list-hosts | head)

Reset SIGPIPE to SIG_DFL at startup so writing to a closed stdout
terminates the process quietly like normal Unix tools, instead of
panicking with "failed printing to stdout: Broken pipe".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011YPrEZVBpPVoCRyJz2exkZ

Cargo.toml

@@ -21,6 +21,9 @@ dirs = "5"
 anyhow = "1"
 chrono = { version = "0.4", default-features = false, features = ["clock", "std"] }
 
+[target.'cfg(unix)'.dependencies]
+libc = "0.2"
+
 [profile.release]
 strip = true
 opt-level = "z"