Fixes: https://github.com/go-gitea/gitea/issues/34865
1. When opening a PR from a branch with multiple commits, use the first
(oldest) commit's title as the default title instead of the branch name
2. Fix autofocus on PR title input field
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>