refactor: ensure type safety of `Cffu`; if return type is `Cffu`, the… #2628

	# Quickstart for GitHub Actions
	# https://docs.github.com/en/actions/quickstart

	name: Strong CI
	on: [ push, pull_request, workflow_dispatch ]
	jobs:
	test:
	# https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#choosing-github-hosted-runners
	runs-on: ubuntu-latest
	timeout-minutes: 15
	name: CI by multiply java versions

	steps:
	- uses: actions/checkout@v4
	with:
	submodules: recursive

	- name: Setup Java
	uses: actions/setup-java@v4
	with:
	# https://github.com/actions/setup-java?tab=readme-ov-file#install-multiple-jdks
	java-version: \|
	8
	11
	17
	21
	22
	distribution: zulu
	cache: maven

	- name: Run integration test
	run: scripts/integration_test
	- name: Run integration of demos
	run: demos/scripts/integration_test

	- name: Remove self maven install files
	run: rm -rf $HOME/.m2/repository/io/foldright/cffu*

	- name: Upload coverage reports to Codecov
	uses: codecov/codecov-action@v4
	env:
	CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

	# https://remarkablemark.org/blog/2017/10/12/check-git-dirty/
	- name: Check git dirty
	run: \|
	git status --short
	[ -z "$(git status --short)" ]

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