feat: add parse_document to the MonkeyOCR transport

Unrecognizable bytes are rejected before any request. The result package is downloaded as a stream with a cumulative size cap, and error statuses are classified before the size check. Parsing runs in a worker thread so cancellation and call deadlines stay effective. parse_layout shares the first protocol stage without behavior change.

tests/unit/_document_fixtures.py

@@ -0,0 +1,71 @@
+"""OCR 文档结果包的合成 fixtures(#34)。
+
+全部**合成**: 保留 2026-10-21 实测的结构骨架(para_blocks 块类型、table/image 的嵌套
+`blocks`、span 字段),一切识别文本替换为 `SYNTH-*` 占位——第三方论文内容许可不明、
+医疗数据不入库(零业务假设 + P5),真实 ZIP 不提交。
+"""
+
+import io
+import json
+import zipfile
+
+_BBOX = (10.0, 20.0, 110.0, 40.0)
+
+
+def _span(content="SYNTH-TEXT", type_="text"):
+    return {"type": type_, "content": content, "bbox": list(_BBOX), "score": 1.0}
+
+
+def _text_block(content="SYNTH-TEXT", *, type_="text", bbox=_BBOX):
+    return {
+        "type": type_,
+        "bbox": list(bbox),
+        "index": 0,
+        "lines": [{"bbox": list(bbox), "spans": [_span(content)]}],
+    }
+
+
+def _body(type_, spans, bbox=_BBOX):
+    return {"type": type_, "bbox": list(bbox), "lines": [{"bbox": list(bbox), "spans": spans}]}
+
+
+def _table_block(html="<table><tr><td>SYNTH-CELL</td></tr></table>", extra_subs=()):
+    body = _body("table_body", [{"type": "table", "html": html, "image_path": "synth.jpg"}])
+    return {"type": "table", "bbox": list(_BBOX), "index": 1, "blocks": [*extra_subs, body]}
+
+
+def _image_block():
+    body = _body("image_body", [{"type": "image", "image_path": "synth.jpg"}])
+    return {"type": "image", "bbox": list(_BBOX), "index": 2, "blocks": [body]}
+
+
+def _page(blocks=None, *, page_idx=0, page_size=(612.0, 792.0), **extra):
+    page = {"page_idx": page_idx, "page_size": list(page_size), "discarded_blocks": []}
+    if blocks is not None:
+        page["para_blocks"] = blocks
+    page.update(extra)
+    return page
+
+
+def _package(
+    pages=None,
+    *,
+    md="# synth\n",
+    middle=None,
+    middle_name="doc_middle.json",
+    md_name=None,
+    extra=(),
+):
+    """组装结果包。`middle` 给原始 bytes 时原样写入;`md_name` 默认由 middle 名配对。"""
+    if middle is None:
+        middle = json.dumps({"pdf_info": pages if pages is not None else [_page([])]}).encode()
+    if md_name is None:
+        md_name = middle_name[: -len("_middle.json")] + ".md"
+    buf = io.BytesIO()
+    with zipfile.ZipFile(buf, "w") as zf:
+        zf.writestr(middle_name, middle)
+        if md is not None:
+            zf.writestr(md_name, md if isinstance(md, bytes) else md.encode())
+        for name, data in extra:
+            zf.writestr(name, data)
+    return buf.getvalue()