Returns the section's content wrapped in a complete HTML document (with <html>, <head>, <body>). Use this when embedding the section in an external viewer or PDF renderer that expects a self-contained HTML page; for the raw content fragment used elsewhere, fetch the section directly via GET /experiments/sections/{expJournalID}. Returns 409 Conflict if the section was edited in the new spreadsheet editor of ELN v2, whose contents are no longer stored in this format.