feat(extract,cli): typography as a PDF heading source and OCR behind an optional group, both off

A PDF carries no notion of a heading -- a heading in a PDF is a typographic
fact -- so the text stream `pdfplumber` hands the segment proposer has already
thrown away the only evidence there was. The `docx` path never had that problem:
the converter emits ATX headings and `_ATX` cuts on them. Two readers close the
gap, and both are OFF.

`--pdf-headings font` infers a heading from the conjunction this repository
already measured (size above the document's character-weighted body median AND
a bold font name, recall 1.000 / precision 0.846) and emits it as ATX in the
SAME markdown the office path produces, so `_ATX` applies unchanged and no
PDF-only heading grammar exists.

It stays off BY MEASUREMENT, and the measurement is the point of the round:
against the operator's unit worksheet it takes `pdf` from 2 of 8 to 0 of 8,
losing two exact matches. The mechanism of the loss is stated rather than
guessed -- on those documents the outline rule already recovers the document's
own numbered chapters, so a second heading source can only add. Whole-corpus
screen: 25 of 32 `pdf` change, 0 of 5 `docx`, 0 of 2 `xlsx`. The default bundle
is byte-identical before and after this commit (`diff -r`, exit 0).

`--ocr` reads a page as an image when its own text never arrived: empty, or
`(cid:N)` placeholder codes at or above a threshold READ OFF a measured
distribution -- 834 pages over 32 files, 818 at exactly 0.0 and 16 at 0.93 or
above, nothing in between. On the one corpus document with the failure: 95.07 %
cid to 0 %, 44 to 2561 words of four or more letters, 17 to 18 pages with text.
Its engine is an optional dependency group and never a runtime dependency; a
packaging test pins both halves, and without the group every affected file is a
coded rejection (`extractor_ocr_group_missing`) rather than a crash.

Also corrects two stale published facts found while measuring: the README still
said two segmentation rules were on by default after `f6fea13` made it three,
and CLAUDE.md's K2 digest named the round-3 default. The current default is
492 concepts / 944 files, `bdefa679...`.

Report: docs/2026-09-08-k3-runde4-pdf-skrift-og-ocr.md

Co-Authored-By: Claude <claude-opus-5>

tests/fixtures/font-heading-krav.pdf

@@ -0,0 +1,39 @@
+%PDF-1.4
+1 0 obj
+<< /Type /Catalog /Pages 2 0 R >>
+endobj
+2 0 obj
+<< /Type /Pages /Kids [3 0 R] /Count 1 >>
+endobj
+3 0 obj
+<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Contents 4 0 R /Resources << /Font << /F1 5 0 R /F2 6 0 R >> >> >>
+endobj
+4 0 obj
+<< /Length 221 >>
+stream
+BT /F2 20 Tf 50 700 Td (Generelle tekniske krav) Tj ET
+BT /F1 10 Tf 50 670 Td (Utkilingen skal ha helning 1:15.) Tj ET
+BT /F2 14 Tf 50 640 Td (Merking) Tj ET
+BT /F1 10 Tf 50 610 Td (Kravet gjelder alle veiklasser.) Tj ET
+endstream
+endobj
+5 0 obj
+<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica /Encoding /WinAnsiEncoding >>
+endobj
+6 0 obj
+<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica-Bold /Encoding /WinAnsiEncoding >>
+endobj
+xref
+0 7
+0000000000 65535 f 
+0000000009 00000 n 
+0000000058 00000 n 
+0000000115 00000 n 
+0000000251 00000 n 
+0000000522 00000 n 
+0000000619 00000 n 
+trailer
+<< /Size 7 /Root 1 0 R >>
+startxref
+721
+%%EOF

tests/fixtures/make_fixtures.py

@@ -51,6 +51,57 @@ PAGED_CONTENTS = (
 )
 
 
+# Two fonts and three sizes on one page: a 20pt bold title, a 14pt bold
+# subheading, and 10pt regular body. The PDF format carries no notion of a
+# heading at all -- a heading in a PDF is a typographic fact, which is why the
+# font-aware reader has to infer one -- so a fixture for that reader must state
+# the typography and nothing else. The body is the majority of the characters,
+# which is what gives the reader a body size to compare against.
+FONT_HEADING_CONTENT = (
+    b"BT /F2 20 Tf 50 700 Td (Generelle tekniske krav) Tj ET\n"
+    b"BT /F1 10 Tf 50 670 Td (Utkilingen skal ha helning 1:15.) Tj ET\n"
+    b"BT /F2 14 Tf 50 640 Td (Merking) Tj ET\n"
+    b"BT /F1 10 Tf 50 610 Td (Kravet gjelder alle veiklasser.) Tj ET\n"
+)
+
+
+def build_two_font_pdf(content: bytes) -> bytes:
+    """A one-page PDF whose resources declare BOTH a regular and a bold font.
+
+    Separate from `build_paged_pdf` rather than a parameter on it: that builder
+    emits exactly one font object and every existing fixture's bytes depend on
+    its object numbering. A second font changes the numbering, so sharing the
+    code would mean regenerating files whose whole value is that they have not
+    moved.
+
+    The page is Letter-sized rather than the 200x200 the other fixtures use,
+    because a 20pt line of this length does not fit inside 200 points and a
+    character laid outside the page box is not one a reader has to see.
+    """
+    objects = [
+        b"<< /Type /Catalog /Pages 2 0 R >>",
+        b"<< /Type /Pages /Kids [3 0 R] /Count 1 >>",
+        b"<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Contents 4 0 R "
+        b"/Resources << /Font << /F1 5 0 R /F2 6 0 R >> >> >>",
+        b"<< /Length " + str(len(content)).encode() + b" >>\nstream\n" + content + b"endstream",
+        b"<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica /Encoding /WinAnsiEncoding >>",
+        b"<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica-Bold /Encoding /WinAnsiEncoding >>",
+    ]
+    out = bytearray(b"%PDF-1.4\n")
+    offsets = []
+    for number, body in enumerate(objects, start=1):
+        offsets.append(len(out))
+        out += str(number).encode() + b" 0 obj\n" + body + b"\nendobj\n"
+    xref_at = len(out)
+    size = str(len(objects) + 1).encode()
+    out += b"xref\n0 " + size + b"\n0000000000 65535 f \n"
+    for offset in offsets:
+        out += ("%010d 00000 n \n" % offset).encode()
+    out += b"trailer\n<< /Size " + size + b" /Root 1 0 R >>\n"
+    out += b"startxref\n" + str(xref_at).encode() + b"\n%%EOF\n"
+    return bytes(out)
+
+
 def build_pdf(content: bytes) -> bytes:
     """Assemble a one-page PDF around `content` as the page content stream."""
     return build_paged_pdf((content,))
@@ -365,6 +416,9 @@ if __name__ == "__main__":
     (HERE / "three-page-krav.pdf").write_bytes(build_paged_pdf(PAGED_CONTENTS))
     print("wrote three-page-krav.pdf")
 
+    (HERE / "font-heading-krav.pdf").write_bytes(build_two_font_pdf(FONT_HEADING_CONTENT))
+    print("wrote font-heading-krav.pdf")
+
     for name, parts in (
         ("two-line-krav.docx", _DOCX_PARTS),
         ("no-styles-krav.docx", _DOCX_NO_STYLES_PARTS),