water/server/scripts/migrate_water_agent_hierarchy.php

<?php
/** Add explicit water-agent hierarchy without inferring legacy organizational levels. */
require dirname(__DIR__).'/vendor/autoload.php';
\Dotenv\Dotenv::createUnsafeMutable(dirname(__DIR__))->load();
\support\App::loadAllConfig(['route']);
use plugin\saiadmin\app\model\water\WaterAgent;
$schema=(new WaterAgent())->getConnection()->getSchemaBuilder();
if (!in_array('--apply',$argv,true)) { echo "Plan: add nullable parent_id to water agents; existing levels remain unconfigured.\n"; exit; }
if (!$schema->hasColumn('sa_water_agent','parent_id')) {
    $schema->table('sa_water_agent',function (\Illuminate\Database\Schema\Blueprint $table) {
        $table->unsignedBigInteger('parent_id')->nullable()->index()->comment('NULL未设置，0一级代理，其余为上级供水代理ID');
    });
}
echo "Applied: agent parent_id available; existing accounts, permissions and business data preserved.\n";