feat: python agent toolkit wrapper + langchain integration

[joshsny]

Create a langchain python integration, and a wrapper package for the MCP server to make it easy for people to use PostHog in langchain agents.

[Copilot]

Pull Request Overview

This PR creates a Python agent toolkit wrapper and LangChain integration for the PostHog MCP server. It transforms the existing Python MCP implementation into a more accessible toolkit that allows developers to easily integrate PostHog tools with LangChain agents.

• Renames the package from posthog-mcp-python to posthog-agent-toolkit with updated dependencies
• Creates a new LangChain integration with PostHogAgentToolkit class that wraps the MCP server
• Adds a complete example implementation showing how to use PostHog tools in a LangChain agent for product usage analysis

Reviewed Changes

Copilot reviewed 11 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
python/pyproject.toml	Updates package metadata and adds LangChain dependencies
python/requirements-test.txt	Removes test dependencies (entire file deleted)
python/posthog_agent_toolkit/	Creates new package structure with toolkit and LangChain integration
examples/langchain/	Adds complete example with configuration, code, and documentation
.github/workflows/publish.yml	Updates CI to specify TypeScript path for package version checking

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[JonathanLab]

LGTM 🚢