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

docs/reference/commands/README.md

@@ -79,7 +79,7 @@ Full records: [provenance.md](provenance.md)
 Full records: [raw-material-and-uploads.md](raw-material-and-uploads.md)
 
 - [`raw fetch`](raw-material-and-uploads.md#raw-fetch) - Capture a web page the user names into `incoming/`: the HTML as received plus a derived text, for `raw accept` to promote.
-- [`raw derive`](raw-material-and-uploads.md#raw-derive) - Derive reading text from a PDF, e-mail, Office file or web page in `incoming/` and leave the original beside it, for `raw accept` to promote.
+- [`raw derive`](raw-material-and-uploads.md#raw-derive) - Derive reading text from a PDF, e-mail, Office file or web page in `incoming/`, or unpack a ZIP, and leave the original beside it, for `raw accept` to promote.
 - [`raw capture`](raw-material-and-uploads.md#raw-capture) - Capture documentation from a git repository into `incoming/<bundle>/`, with a manifest naming the repository, ref rule and commit, for `raw accept` to promote.
 - [`raw status`](raw-material-and-uploads.md#raw-status) - Report which captured bundles under `raw/` have fallen behind their repository, with each changed file as `A`/`M`/`D`.
 - [`raw pending`](raw-material-and-uploads.md#raw-pending) - List what waits in `incoming/`, oldest first, and name the entry an ingest without an argument takes next.