* feat(export): add simple HTML mode
* test(automation): reject simple HTML mode for other formats
* test(export): check simple HTML without new parser dev-dependencies
The parser test pulled html5ever, markup5ever_rcdom and seven more crates
into Cargo.lock for one test; plain string checks cover the same markup.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>