feat(raw): raw derive reads PDF and Outlook MSG; doctor shows each import filter

PDF is read with pypdf (page markers, scan warning, encrypted files refused), Outlook .msg with olefile as a container like an .eml, and a .msg attached to a mail is quoted. Both packages are in tools/requirements.txt and imported only when such a file is derived, so a missing one stops that format alone. doctor reports one import-filter line per package-backed format.

Files changed:
- CHANGES.md
- VERSION
- docs/how-to/ingest-a-source.md
- docs/reference/commands/instance-health.md
- docs/reference/commands/raw-material-and-uploads.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/raw_cmd.py
- tools/chemenu/filters/__init__.py
- tools/chemenu/filters/mail.py
- tools/chemenu/filters/msg.py
- tools/chemenu/filters/pdf.py
- tools/chemenu/tests/binary_formats.py
- tools/chemenu/tests/test_raw_derive_binary.py
- tools/requirements.txt

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

CHANGES.md

@@ -14,7 +14,7 @@ place only: `instructions/dev/version-parts.md` § The candidate model.
 
 ---
 
-## 9.0.0-beta.15 - 2026-10-08 - raw derive unpacks ZIP archives and mails with attachments into a folder
+## 9.0.0-beta.16 - 2026-10-08 - raw derive reads PDF and Outlook MSG through lazily imported packages; doctor shows each import filter
 
 **Author:** Torben Nehmer
 
@@ -37,6 +37,7 @@ place only: `instructions/dev/version-parts.md` § The candidate model.
 - Asset-Preflight: Verschieben aus dem Entpackordner wird bis ca. 30 s wiederholt, nennt die Systemmeldung und rollt nach endgültigem Scheitern zurück
 - raw derive reads PDF-free documents: Office files and mail become a folder with the original and a derived text
 - raw derive unpacks ZIP archives and mails with attachments into a folder
+- raw derive reads PDF and Outlook MSG through lazily imported packages; doctor shows each import filter
 
 **Low impact**
 - version bump: Abschlussmeldung nennt Stichpunkt oder Themenabsatz statt pauschal Prosa