test(extract): hand-built office fixtures with frozen extracted text

Three hand-laid OOXML containers, every part written out by hand and zipped
with a fixed date_time so they are byte-reproducible. No converter output
anywhere in them: a .docx written by the converter and read by the converter
proves only that the converter agrees with itself, and would stay green through
any conversion defect that is symmetric -- which is most of them.

  two-line-krav.docx    heading + label/value on one line (the docx mirror of
                        the PDF fixture)
  no-styles-krav.docx   the SAME document without word/styles.xml
  two-line-krav.xlsx    sheet name as heading + label/value on one row

THE FIXTURES FOUND A REAL DEFECT IN THE SEAM THEY WERE MEANT TO PIN. The
converter call used pypandoc's TEXT entry point, which takes an `encoding`
because it treats its source as text -- and that corrupts a zip. The xlsx
fixture failed with `Failed to unpack XLSX archive: not enough bytes` while
reading correctly from disk with the same binary. The docx of the same shape
happened to survive, which is the part worth writing down: the defect is silent
for some inputs and fatal for others, so "it worked on the file I tried" was
never evidence. Input now goes through a temporary file.

Two measurements while building, both the same shape -- structurally valid
input, silently reduced output, exit code 0, no warning:

- Without word/styles.xml the docx extracts as flat prose with no heading. A
  fixture lacking that part would pin the body and pin nothing about structure.
  Committed as a negative control that RUNS rather than a sentence in a README.
- With inline strings rather than a shared string table, the xlsx extracts with
  the sheet name intact and every cell value gone. The fixture uses a dimension
  element and a shared string table instead.

The frozen literals are pinned to a NAMED converter version, asserted beside
them: a frozen literal without one says "these bytes" without saying what
produced them.

Suite 908 -> 913. Fixtures regenerate byte-identically.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_extract.py

@@ -310,6 +310,87 @@ def test_office_conversion_warns_that_it_is_lossy(
 # a parser upgrade break something visible instead of drifting silently.
 KRAV_TEXT = "Krav til helning på utkilingen\n60 og 70 1:15"
 
+# The office fixtures are frozen the same way, and against a NAMED converter
+# version -- a frozen literal means nothing without one, because the thing it
+# pins is "this converter, on this input, produces these bytes". `_pandoc.py`
+# refuses any other version, so the two pins hold each other up.
+requires_pandoc = pytest.mark.skipif(
+    importlib.util.find_spec("pypandoc") is None,
+    reason="the optional [extract] extra is not installed",
+)
+
+# docx: a heading and one requirement row with label and value on the SAME
+# line, mirroring the property the PDF fixture pins.
+DOCX_TEXT = "# Krav til helning\n\n60 og 70 1:15"
+
+# xlsx: the sheet name becomes a heading and the rows become a table. The
+# label/value pairing survives on one row, which is the property that matters.
+XLSX_TEXT = (
+    "## Krav {#sheet-1}\n\n  Krav til helning   \n"
+    "  ------------------ ------\n  60 og 70           1:15"
+)
+
+# The negative control, committed rather than described: the SAME document
+# without `word/styles.xml`. The body survives and the heading marker does not.
+DOCX_NO_STYLES_TEXT = "Krav til helning\n\n60 og 70 1:15"
+
+
+@requires_pandoc
+def test_docx_extracts_to_its_frozen_text() -> None:
+    data = (FIXTURES / "two-line-krav.docx").read_bytes()
+    with pytest.warns(ExtractionWarning):
+        assert extract_text("krav.docx", data) == DOCX_TEXT
+
+
+@requires_pandoc
+def test_xlsx_extracts_to_its_frozen_text() -> None:
+    data = (FIXTURES / "two-line-krav.xlsx").read_bytes()
+    with pytest.warns(ExtractionWarning):
+        assert extract_text("krav.xlsx", data) == XLSX_TEXT
+
+
+@requires_pandoc
+def test_a_docx_without_a_styles_part_loses_its_heading() -> None:
+    """The negative control for the fixture policy, run rather than asserted.
+
+    `word/styles.xml` is what makes the converter see a heading. Without it the
+    same document extracts as flat prose -- so a fixture built WITHOUT that
+    part would pin the body and pin nothing at all about structure, while
+    looking exactly as convincing.
+
+    Structure is the half the segment proposer reads, which is why this is a
+    committed fixture and not a sentence in a README.
+    """
+    data = (FIXTURES / "no-styles-krav.docx").read_bytes()
+    with pytest.warns(ExtractionWarning):
+        text = extract_text("krav.docx", data)
+    assert text == DOCX_NO_STYLES_TEXT
+    assert not text.startswith("#"), "the heading marker must be absent"
+    assert DOCX_TEXT.startswith("#"), "and present in the fixture that has styles"
+
+
+@requires_pandoc
+def test_the_frozen_office_text_is_pinned_to_a_named_converter_version() -> None:
+    """A frozen literal without a named version pins nothing.
+
+    If the converter version ever moves, these literals must be re-measured
+    rather than trusted -- so the version is asserted right where they live.
+    """
+    from llm_ingestion_okf._pandoc import PANDOC_VERSION, resolve_pandoc
+
+    assert PANDOC_VERSION == "3.9"
+    assert resolve_pandoc().is_file()
+
+
+@requires_pandoc
+def test_office_extraction_is_byte_stable_across_calls() -> None:
+    data = (FIXTURES / "two-line-krav.docx").read_bytes()
+    with pytest.warns(ExtractionWarning):
+        first = extract_text("krav.docx", data)
+    with pytest.warns(ExtractionWarning):
+        second = extract_text("krav.docx", data)
+    assert first == second
+
 
 @requires_extract
 def test_pdf_extracts_text_with_label_and_value_on_one_line() -> None: