Add Mathpix MMD/lines/images for documents/10.1056_nejmoa1801005

Adds Mathpix-converted outputs for `documents/10.1056_nejmoa1801005`:

- `*.mmd` — Mathpix Markdown (text + math + tables)
- `*.lines.json` — line-level OCR/layout data
- `images/` — figures referenced by the `.mmd` via `./images/<name>`

Generated from the source PDFs already in this dataset. Where a folder's `protocol.pdf` and `sap.pdf` are byte-identical (a combined Protocol+SAP document), a `DEDUP_NOTE.md` explains the duplication.

documents/10.1056_nejmoa1801005/DEDUP_NOTE.md

@@ -0,0 +1,7 @@
+# Identical source PDFs
+
+`protocol.pdf` and `sap.pdf` in this folder are **byte-identical** (sha256 `909d07cdb5631ac51002e618219a918c77671a8978169ebd351d04652c5cc74c`).
+
+The trialdesignbench source for this trial is a single combined Protocol+SAP document, which the dataset stores under both names. Because the inputs are the same file, their converted outputs (`*.mmd`, `*.lines.json`) are identical and were produced from one Mathpix conversion; the `images/` figures are shared.
+
+Generated by healthtech/trialdesignbench/convert_hf_documents.py