v0.0.27

Fixed

• Two-column papers are no longer read across the columns. Extraction
  passed -layout to pdftotext, which preserves the visual arrangement:
  on a two-column paper the left and right columns were spliced onto shared
  lines, so sentences broke mid-thought and merged with unrelated text. Since
  a claim survives verification only when its SOURCE_QUOTE appears verbatim
  in the source, this quietly undermined grounding on exactly the documents
  the tool is built for. Poppler's default reading order is now used. Measured
  on a real corpus, spliced lines fell from 158 and 59 on two papers to zero
  on all of them.
• A contents listing no longer truncates the whole paper. Sectioning cut
  the document at the first line matching references|bibliography| acknowledgements|appendix, which in a paper with a contents page is the
  entry "References … 4" in the front matter, not the bibliography. A 62-page
  paper was reduced to its first 8kB — the claim ledger was built from the
  table of contents. The last such heading is now used, which also keeps the
  degenerate case right: a document that is only a bibliography still yields
  no sections. The same paper now retains 97.3% of its text, up from 3.9%.

Added

• A clear diagnosis for PDFs with no text layer. A scan or image export
  previously produced empty text and a late, vague failure. pdf.ErrNoTextLayer
  now explains what happened and what to do — run OCR, or supply a text source.
• Real PDF fixtures. internal/pdf/testdata holds a generated two-column
  paper — complete with a contents listing naming "References" in its front
  matter — and a page with no text layer, both built by a committed script so
  they are reproducible and license-clean. Regression tests assert that no
  output line carries text from two columns, that body claims survive
  sectioning, that the real bibliography is still dropped, and that a
  text-less PDF is diagnosed.