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

instructions/wiki-ingest/SKILL.md

@@ -46,6 +46,8 @@ validator complains - and the ticked list is the only record that they happened.
    the normal path, or already under `raw/` when the run started there (a file `capture-session`
    just wrote, for instance, which skips step 5 entirely). A PDF, mail, Office file or ZIP: run
    `tools/wikitool raw derive <path>` first and read the `.md` - its output names what to check.
+   A PDF whose `derived.md` header has an `images:` or `unmatched:` field names pages the text
+   does not hold: `instructions/read-page-images.md` decides which of them are looked at, and how.
    Any other binary or image: note its presence and what it shows.
 
    **The user named nothing** ("ingest", "process the inbox")? First pull what the configured
@@ -365,7 +367,8 @@ validator complains - and the ticked list is the only record that they happened.
    `kb/CONTRACT.md` § Language and identifiers.
 
    Fill `## Not Extracted` in the same pass: what you read and deliberately did not promote,
-   with the reason. Nothing in the repository can re-derive that judgment, and without it the
+   with the reason - including the selected page images nobody looked at
+   (`instructions/read-page-images.md`). Nothing in the repository can re-derive that judgment, and without it the
    same source gets re-litigated on the next pass.
 
 7. **Create or update entity pages.** Read