Fixes #

Changes

• Require PR-body changelog details instead of accepting arbitrary unreleased changelog files.
• Keep release changelog PR association mandatory while making branch-named legacy entries resolvable through GitHub's commit-to-PR API.
• Add dry-run support to release prep and local release scripts.

Testing instructions

• composer check-cs
• bash -n bin/changelog-write.sh
• bash -n bin/version-bump.sh
• bash -n bin/changelog-add.sh
• ruby -e 'require "yaml"; %w[.github/workflows/changelog.yml .github/workflows/release-prep.yml].each { |f| YAML.load_file(f); puts "#{f} parsed" }'
• git diff --check

Changelog entry

• Automatically create a changelog entry from the details below.