feat(documents): markkit as default Office converter, deprecate office

[chaliy]

What changed

markkit (0.1.0, crates.io) becomes the default Office backend. The in-crate office converter from #181 is deprecated and off by default.

• New docs-markkit feature, on by default. It adds MarkkitConverter (name markkit, local) for DOCX, XLSX/XLSM, XLS and ODS.
  • Extraction methods are markkit_docx, markkit_xlsx, markkit_xls and markkit_ods.
  • Limits are tuned with MarkkitConverter::with_markkit(Markkit::builder()…). Markkit and MarkkitBuilder are re-exported from fetchkit::documents.
• Feature defaults: docs-pdf + docs-office becomes docs-pdf + docs-markkit. docs-all now includes markkit and excludes office.
• OfficeConverter is #[deprecated]. It still works behind docs-office, and when that feature is enabled it runs after markkit as a fallback.
• Settings, CLI and Python: --converter markkit / converters=["markkit"] are accepted. When a feature is missing, the error says so.
• markkit is built without its HTTP client, and the only reqwest in the tree is fetchkit's own.

Why

The repo owner decided that #181's in-crate Office parsing is not the implementation to keep. Office parsing moves to markkit, which fetchkit's design already planned as a pluggable backend. markkit has zip-bomb, archive and spreadsheet-grid limits, and it skips hidden sheets by default.

Before / After

Before (default build): fetchkit fetch …/demo.docx gave extraction_method: "office_docx".

After:

$ fetchkit fetch https://calibre-ebook.com/downloads/demos/demo.docx
quality_score: 1.00
extraction_method: "markkit_docx"
---
# Demonstration of DOCX support in calibre
…
| ITEM | NEEDED |
| Books | 1 |

Local files: .xlsx gives markkit_xlsx (with a hidden_sheet_skipped warning), .xls gives markkit_xls, .ods gives markkit_ods, and a large sheet carries a truncated_sheet warning. Legacy .doc is still rejected with "DOC conversion is not enabled".

Risk

• Medium. Unreleased API change on top of feat(documents): pluggable document conversion with converter chain #182.
• PPTX and XLSB are no longer converted by default, because markkit doesn't support them yet. Enabling docs-office restores them.
• Spreadsheet titles are no longer extracted.
• markkit's default sheet caps are looser: 10,000 rows × 256 columns, where office used 1,000 × 50. Output is still capped by max_body_size.
• New transitive crates: cfb, uuid, regex, anyhow, mime, unicode-segmentation.

Checklist

• Unit tests are passed: cargo test --workspace, plus feature sets with no defaults, docs-markkit only, and docs-all,docs-office. clippy -D warnings passes across the same sets.
• Smoke tests are passed: the release CLI on a real DOCX, and local XLSX/XLS/ODS files.
• Documentation is updated: README, CHANGELOG (Added and Deprecated), docs/hardening.md.
• Knowledge is up to date and not in conflict: fetchers, tool contract, TM-DOS-008, and the log. check_okf.py passes.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Y2vd61x8kbPtmDxze9Q4Gi

---

Generated by Claude Code