The previous `read_text(encoding="utf-8")` call left the UTF-8 byte
order mark (EF BB BF, three bytes) in the content string if the file
was saved by a tool that emits a BOM. The first line check
(`lines[0].strip() != "---"`) then saw "\ufeff---" and rejected the
file as "Invalid frontmatter format", even though the document was
otherwise valid frontmatter.
Co-authored-by: Zo Bot <github-automation@zo.computer>
6567f99625