Fix: pgvector pg import compatibility with Node ESM

Problem

In the OSS bundle, the pgvector vector store imports pg like this:

import { Client } from "pg";

But pg is a CommonJS module. Under Node ESM, it does not provide named exports, so module evaluation fails with:

SyntaxError: Named export 'Client' not found. The requested module 'pg' is a CommonJS module

This breaks downstream integrations (e.g. OpenClaw Mem0 plugin) because the OSS bundle throws during import, causing memory capture and recall to fail.

Solution

Switch to a CJS-safe ESM import style:

import type { Client as ClientType } from "pg";
import pkg from "pg";
const { Client } = pkg;

private client: ClientType;

Testing

• Node: v22.22.0
• pnpm test in mem0-ts/ ✅

Closes: #4543