Prepare push repository logic to anywherephp/jack

[TomasVotruba]

Same change as rectorphp/type-perfect#75, mirroring TomasVotruba/type-coverage@6474f96.

The Downgraded Release workflow now builds the PHP 7.2 downgraded + scoped code and pushes it to https://github.com/anywherephp/jack (already seeded with a main branch), instead of force-pushing downgraded tags back into this repository:

• trigger on main pushes (updates remote main) and on tags (pushes a tag to the remote repository)
• the build mechanics are kept as-is: composer update --no-dev, rector-local downgrade of bin src vendor, prefix-code.sh scoping
• build/target-repository/composer.json renamed to anywherephp/jack + proprietary license
• added README.md and auto_closer.yaml pointing back here, removed FUNDING.yml

Jack-specific details:

• the remote .gitignore is removed before committing, because it ignores /vendor — and this scoped build ships its vendor
• kept bare_run.yaml in the target repository — it runs bin/jack from checkout on PHP 7.2–8.2, so it smoke-tests every pushed build (unlike type-perfect's standalone_install.yaml, it does not depend on Packagist)
• also stops shipping composer.lock and composer-dependency-analyser.php in the build

⚠️ Notes:

• this replaces the self-tagging downgraded release of rector/jack
• requires the WORKFLOWS_TOKEN secret (already used by the old workflow) to have push access to the anywherephp org