Add Cython build infra + initial extension module #64

	name: Validate Source Rules
	on:
	push:
	branches:
	- main
	pull_request:

	concurrency:
	group: check-${{github.ref}}
	cancel-in-progress: true

	jobs:
	lint:
	name: Check Source Code
	runs-on: ubuntu-latest

	steps:
	- name: 📥 Check out source code
	uses: actions/checkout@v4
	with:
	fetch-depth: 0

	- name: 🐍 Set up Python
	uses: actions/setup-python@v4
	with:
	python-version: "3.11"
	cache: "pip"

	- name: 🛠️ Install development tools and dependencies
	run: \|
	pip install -e .[dev]

	- name: 🪮 Check source code formatting
	id: format
	run: \|
	if ruff format --diff $PKG_DIR; then
	echo passed=yes >>"$GITHUB_OUTPUT"
	else
	echo passed=no >>"$GITHUB_OUTPUT"
	echo "::error::source code not formatted"
	fi
	env:
	PKG_DIR: lenskit

	- name: 🐜 Check source code lint rules
	id: lint
	run: \|
	if ruff check --output-format=github $PKG_DIR; then
	echo passed=yes >>"$GITHUB_OUTPUT"
	else
	echo passed=no >>"$GITHUB_OUTPUT"
	echo "::error::source code lint check failed"
	fi
	env:
	PKG_DIR: lenskit

	- name: 🧾 Checking lint and format results
	run: \|
	if [ "$FMT_PASSED" = no ]; then
	echo "::error::format failed, failing build"
	exit 1
	fi
	if [ "$LINT_PASSED" = no ]; then
	if [ "$LINT_REQUIRED" = true ]; then
	echo "::error::lint failed, failing build"
	exit 2
	else
	echo "::error::lint failed but non-mandatory"
	fi
	fi
	env:
	FMT_PASSED: ${{ steps.format.outputs.passed }}
	LINT_PASSED: ${{ steps.lint.outputs.passed }}
	LINT_REQUIRED: False

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