XAI Live Search API will be deprecated, use tools instead

### Checked other resources - [x] This is a feature request, not a bug report or usage question. - [x] I added a clear and descriptive title that summarizes the feature request. - [x] I used the GitHub search to find a similar feature request and didn't find it. - [x] I checked the LangChain documentation and API reference to see if this feature already exists. - [x] This is not related to the langchain-community package. ### Package (Required) - [ ] langchain - [ ] langchain-openai - [ ] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [ ] langchain-cli - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [ ] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-perplexity - [ ] langchain-prompty - [ ] langchain-qdrant - [x] langchain-xai - [ ] Other / not sure / general ### Feature Description https://docs.x.ai/docs/guides/tools/overview The advanced agentic search capabilities powering grok.com are generally available in the new [agentic tool calling API](https://docs.x.ai/docs/guides/tools/overview), and the Live Search API will be deprecated by December 15, 2025. ### Use Case Since it's about to be deprecated, I hope to migrate to the new method as soon as possible, but it's not yet supported. I tried to use the `openai` package instead, but unfortunately it didn't work. The names of the tools are inconsistent, and the server tools names in `openai` are checked. ### Proposed Solution _No response_ ### Alternatives Considered _No response_ ### Additional Context _No response_