feat(nixos): migrate system configuration

configs/nixos/modules/agents/claude-code/hooks/agent-sudo-guard.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+# Refuse a privileged command while sudo's credential cache is cold, naming the
+# command that warms it.
+#
+# Commands arrive here from subprocesses holding no terminal, so an uncached
+# sudo fails with a bare non-zero exit and no output, reading as an unexplained stall.
+# The probe below reads a cache keyed per user rather than per terminal,
+# so an authentication made in the operator's own terminal counts.
+
+input=$(cat)
+command=$(printf '%s' "$input" | jq -r '.tool_input.command // ""')
+
+# Anchored to a command position so a `sudo` appearing as an argument or inside
+# a string does not trip the guard.
+if ! printf '%s' "$command" | grep -qE '(^|[;&|(]|&&|\|\|)[[:space:]]*sudo([[:space:]]|$)'; then
+	exit 0
+fi
+
+if sudo -n true 2>/dev/null; then
+	exit 0
+fi
+
+# Exit 2 blocks the call and feeds stderr back to the agent.
+echo 'Blocked: sudo has no cached credential, and this command cannot answer a password prompt.
+Ask the operator to run `sudo -v` in their own terminal, then retry.
+Never attempt to supply a password directly.
+If this still blocks immediately after the operator runs `sudo -v`, the cache is
+not the cause: check that this hook can reach sudo at all.' >&2
+exit 2