[Feature Request]: MCP Tasks

MCP Protocol [added Tasks as an experimental feature](https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/tasks#tasks). The're part of a larger MCP initiative to become [Stateless-by-default](https://modelcontextprotocol.io/development/roadmap#priority-areas-for-the-next-release) (see first 2 paragraphs). Furthermore, basic Task lifecycle is [already implemented in FastMCP](https://github.com/jlowin/fastmcp/issues/2568) too. However, there is no way to test these with langchain. Can this feature be added please?