feat: automatically update pre-commit config with posthog package for Python projects

[rnegron]

Summary

• Adds a new wizard step that updates .pre-commit-config.yaml (if available) to include the posthog Python package in additional_dependencies (for type-checking hooks, i.e mypy, pyright, pytype).
• Currently only runs on supported Python frameworks: Django, Flask, FastAPI, and (of course) Python

Background

I ran the PostHog wizard on a local Django project and everything worked great! Except that my pre-commit mypy hook failed... Adding this step to hopefully solve for anyone else that might run into this in the future!

Test plan

• Manually tested on said Django project via pnpm link --global in this repo and then wizard --region us in the local Django project.

Here is a snippet of final wizard output (see last point):

Successfully installed PostHog!

What the agent did:
• Analyzed your Django REST Framework project structure
• Installed the PostHog Python package
• Configured PostHog in your Django settings
• Added PostHog middleware for automatic event tracking
• Added environment variables to .env file
• Updated .pre-commit-config.yaml with posthog dependency

[Copilot]

Pull request overview

Adds a new wizard step to automatically update an existing pre-commit configuration for Python projects so type-checking hooks include the posthog package in additional_dependencies, preventing mypy/pyright/pytype failures after installing PostHog.

Changes:

• Added updatePreCommitConfigStep to parse .pre-commit-config.(yml|yaml) and append posthog to relevant hooks’ additional_dependencies.
• Wired the new step into the agent runner for Python integrations (Django/Flask/FastAPI/Python) and reflected it in the wizard outro.
• Added Jest test coverage and introduced the yaml dependency.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/steps/update-pre-commit-config.ts	Implements YAML parsing + mutation of pre-commit config to add posthog to type-checking hooks.
src/steps/index.ts	Exports the new step from the steps barrel.
src/steps/tests/update-pre-commit-config.test.ts	Tests config discovery, idempotency, formatting preservation, and error paths.
src/lib/agent-runner.ts	Runs the new step for Python integrations and includes it in the outro changes list.
package.json	Adds yaml as a direct dependency.
pnpm-lock.yaml	Locks the new yaml dependency/version.

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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[rnegron]

by the way, I am aware there is some ongoing work around how the wizard handles .env files (#263), and this step is effectively modeled after that existing add-or-update-environment-variables step.

I think pre-commit config files are less of a concern than env files when it comes to security and exposure, so I figured I would submit this change anyway in case it would be useful!