Merge development into feature/publish-email-gem

development moved gem PR checks out of release-sdk-gem.yml and into ci.yml (#92), so drop the sdk/gems path triggers from the release workflow and add the email gem to the ci.yml filter and the cross-build, smoke-test and source-gem matrices instead. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>