feat(openai): support web search tool

[christian-bromann]

This PR adds support for OpenAI's web search tool, enabling models to search the web for up-to-date information before generating responses.

Usage

import { ChatOpenAI, tools } from "@langchain/openai";

const model = new ChatOpenAI({ model: "gpt-4o" });

// Basic usage
const response = await model.invoke("What are today's top news stories?", {
  tools: [tools.webSearch()],
});

// With options
const response = await model.invoke("Local weather forecast", {
  tools: [tools.webSearch({
    userLocation: {
      type: "approximate",
      country: "US",
      city: "San Francisco",
    },
    filters: { allowedDomains: ["weather.gov"] },
  })],
});

[changeset-bot]

🦋 Changeset detected

Latest commit: 6b2cf1c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@langchain/openai	Patch
@langchain/classic	Patch
@langchain/community	Patch
@langchain/deepseek	Patch
@langchain/xai	Patch

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