raw derive PDF: Kopf nennt Bildseiten (images) und nicht zugeordnete Seiten (unmatched); neue Anweisung read-page-images für den gezielten Blick auf diese Seiten, Schwelle 20 Seiten (#234); 10.1.0-beta.7

Files changed:
- CHANGES.md
- VERSION
- docs/how-to/ingest-a-source.md
- docs/reference/commands/raw-material-and-uploads.md
- instructions/ingest-large-tree.md
- instructions/read-page-images.md
- instructions/wiki-ingest/SKILL.md
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/chemenu/commands/raw/derive.py
- tools/chemenu/filters/pdf.py
- tools/chemenu/filters/pdf_layout.py
- tools/chemenu/tests/test_raw_derive_binary.py
- types/source.guidance.md

Co-Authored-By: Claude Code <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

docs/how-to/ingest-a-source.md

@@ -51,7 +51,8 @@ pick a directory:
   text (`~~…~~`, `**…**`, `*…*`) with a legend in the header, and what a colour means is for the
   reader to take from the document itself. The tool marks sparingly, in running text and
   not in code or tables. Pages with pictures or drawings that carry content are named in a `CHECK`
-  line, because the pictures are not in the text.
+  line and in the header of the text (`images`), because the pictures are not in the text; the
+  pages whose text could not be matched to the layout are named there too (`unmatched`).
 - **A page behind a paywall or a login** is saved from your browser into `incoming/`, HTML only. The
   agent derives the same text from that file with `raw fetch --html`. For a website you read often,
   sign in once instead and let the wiki fetch it with your session:
@@ -79,6 +80,13 @@ what is waiting and names the entry the next bare `Ingest` will take.
   (`fidelity`) and what the material may claim about its subject (`authority`). Both are recorded
   once and never guessed: you know the answers now, and nobody can recover them later.
   [raw/CONTRACT.md](../../raw/CONTRACT.md) defines the values.
+- **Before looking at page images**, when a PDF names more than 20 pages the text does not hold.
+  The agent reads up to 20 such pages on its own, through a subagent where the harness has one,
+  and records what it saw on the source page, with the page number and the note that it was read
+  from the image. For more pages it reads none first: it tells you the count and a token
+  estimate, proposes a selection, and you choose all, none or a selection. Pages nobody looked at
+  are listed with the reason. Only whole pages are read; a harness that cannot show PDF pages as
+  images gets the page numbers named instead.
 - **Before writing pages**, the agent presents the key takeaways and asks which points matter most
   and what to emphasise. The pages follow your answer.
 - **When it publishes**, a source that touches ten or more files stops at the Mass-Update Gate