feat(raw): raw derive turns Office files and mail into a folder with the original and a derived text

Adds the import-filter registry (tools/chemenu/filters), the raw derive command with folder form,
path-budget and name checks, DOCX/PPTX/XLSX and EML filters, the pending and accept hints, the
wiki-ingest skill step and the raw/CONTRACT.md section. First of three cuts; containers and
PDF/MSG follow.

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
- instructions/wiki-ingest/SKILL.md
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/cli_contract.py
- tools/chemenu/commands/raw_cmd.py
- tools/chemenu/filters/__init__.py
- tools/chemenu/filters/html_page.py
- tools/chemenu/filters/mail.py
- tools/chemenu/filters/ooxml.py
- tools/chemenu/tests/test_raw_derive.py
- tools/chemenu/web_capture.py

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

tools/README.md

@@ -112,6 +112,7 @@ tools/
     kb_state.py            the KB version (.wikitool-kb.json) and the migration chain
     corpus_diff.py         invariant comparison of kb/ between two revisions
     web_capture.py         `raw fetch`'s core: fetch a page, decide its charset, derive Markdown-like text from the HTML - standard library only, deterministic
+    filters/               the import filters behind `raw derive`: a registry (`__init__.py`) and one module per format family (HTML, mail, Office), each registering the extensions it reads - standard library, or a package imported lazily so a missing one fails only its own format
     repo_capture.py        `raw capture`/`raw status`'s core: resolve a ref rule, fetch it into a bare cache, select files by glob as blobs, the `_capture.json` manifest - git with the host's credentials, never a prompt; plus the one write back, a single-file commit pushed without force for `export guidelines`
     guideline_export.py    `export guidelines`' core: select pages by `search` predicates, render them into one deterministic GUIDELINES.md, and recognise an export again (`EXPORT_MARKER`) - with no CLI attached
     search/                pluggable search backends, plus service.py - the search core