fix(drift-check): handle SIGPIPE so | head does not traceback

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Xefg5EXwcpd9RMAr63dWrD

scripts/governance-drift-check.py

@@ -18,11 +18,17 @@ report, not a gate.
 import json
 import os
 import re
-import subprocess
+import signal
 import sys
 from datetime import date
 from pathlib import Path
 
+# Report cleanly when the reader closes early (`| head`), rather than tracebacking.
+try:
+    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+except (AttributeError, ValueError):  # not POSIX, or not on the main thread
+    pass
+
 HOME = Path.home()
 CLAUDE_MD = HOME / "dotfiles" / "CLAUDE.md"
 MONTHS = ("january february march april may june july august september "