feat(raw): raw derive unpacks ZIP archives and mails with attachments into a folder

A ZIP becomes incoming/<stem>/ with its files and a derived text beside each
document, the ZIP is removed and its sha256 named in the output. A mail with
attachments becomes a folder with original.eml, derived.md and the attachments;
a ZIP attached to a mail is unpacked once, an attached mail is quoted. Unsafe
entries, nested ZIPs and size limits are refused before anything is written.

Files changed:
- CHANGES.md
- VERSION
- docs/how-to/ingest-a-source.md
- docs/reference/commands/README.md
- docs/reference/commands/raw-material-and-uploads.md
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/commands/raw_cmd.py
- tools/chemenu/filters/__init__.py
- tools/chemenu/filters/archive.py
- tools/chemenu/filters/mail.py
- tools/chemenu/tests/test_portability.py
- tools/chemenu/tests/test_raw_derive.py

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.14 - 2026-10-08 - raw derive reads PDF-free documents: Office files and mail become a folder with the original and a derived text
+## 9.0.0-beta.15 - 2026-10-08 - raw derive unpacks ZIP archives and mails with attachments into a folder
 
 **Author:** Torben Nehmer
 
@@ -36,6 +36,7 @@ place only: `instructions/dev/version-parts.md` § The candidate model.
 - Gate-Liste: AGENTS.md § Gates ist die eine Liste (mit Rebase-Review Gate), cli_contract.GATES hält sie, docs verify vergleicht beide
 - 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
 
 **Low impact**
 - version bump: Abschlussmeldung nennt Stichpunkt oder Themenabsatz statt pauschal Prosa