chore: add overnight helper scripts

- add morning report launcher\n- add overnight stop script\n- add watchdog health monitor script\n\nRefs #137

scripts/watchdog.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+# Simple watchdog for The Ouroboros process.
+
+set -euo pipefail
+
+PID_FILE="${PID_FILE:-data/overnight/app.pid}"
+LOG_FILE="${LOG_FILE:-data/overnight/watchdog.log}"
+CHECK_INTERVAL="${CHECK_INTERVAL:-30}"
+STATUS_EVERY="${STATUS_EVERY:-10}"
+
+mkdir -p "$(dirname "$LOG_FILE")"
+
+log() {
+    printf '%s %s\n' "$(date -u +"%Y-%m-%dT%H:%M:%SZ")" "$1" | tee -a "$LOG_FILE"
+}
+
+if [ ! -f "$PID_FILE" ]; then
+    log "[ERROR] pid file not found: $PID_FILE"
+    exit 1
+fi
+
+PID="$(cat "$PID_FILE")"
+if [ -z "$PID" ]; then
+    log "[ERROR] pid file is empty: $PID_FILE"
+    exit 1
+fi
+
+log "[INFO] watchdog started (pid=$PID, interval=${CHECK_INTERVAL}s)"
+
+count=0
+while true; do
+    if kill -0 "$PID" 2>/dev/null; then
+        count=$((count + 1))
+        if [ $((count % STATUS_EVERY)) -eq 0 ]; then
+            log "[INFO] process alive (pid=$PID)"
+        fi
+    else
+        log "[ERROR] process stopped (pid=$PID)"
+        exit 1
+    fi
+    sleep "$CHECK_INTERVAL"
+done