fix: restore minimal long-task watchdog execution chain

scripts/install_long_task_watchdog_cron.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+CRON_FILE="$ROOT_DIR/state/cron/long-task-watchdog.cron"
+LOG_DIR="$ROOT_DIR/state/long-task-watchdog"
+RUNNER="$ROOT_DIR/scripts/long_task_watchdog.mjs"
+STATE_FILE="$ROOT_DIR/memory/watchdog-state.json"
+
+mkdir -p "$(dirname "$CRON_FILE")" "$LOG_DIR"
+
+cat >"$CRON_FILE" <<EOF
+*/10 * * * * cd "$ROOT_DIR" && /usr/bin/env node "$RUNNER" --write-state --state "$STATE_FILE" --evidence-dir "$LOG_DIR" >> "$LOG_DIR/cron.log" 2>&1
+EOF
+
+printf 'Wrote cron snippet: %s\n' "$CRON_FILE"
+printf 'To install for current user, run:\n'
+printf '  (crontab -l 2>/dev/null; cat "%s") | crontab -\n' "$CRON_FILE"