Check if git hooks are set up #19
Description
Some projects rely on git hooks to run linting or tests before commits. Check if they are configured:
- Node → check if husky is set up (.husky directory exists)
- Python → check if pre-commit is installed and .pre-commit-config.yaml exists
Return a warning (not a failure) if missing — hooks are optional but good to have.
Add internal/check/githooks.go, register under stack.Node and stack.Python.