chore(release): plugin.json version 0.20.0

New skill (document-to-markdown) is a minor bump; the gate asserts
manifest/tag parity, so this lands with the tag.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "skills",
   "description": "Mathias's engineering skills library, plus the hooks and MCP servers that make it enforceable: TDD, clean code, debugging, specs, discovery, CI, and secret hygiene.",
-  "version": "0.19.5",
+  "version": "0.20.0",
   "author": {
     "name": "Mathias",
     "url": "https://git.d-ma.be/mathias"

SKILLS_INDEX.md

@@ -17,6 +17,7 @@ the SKILL.md, not the table.
 | `cognitive-load` | Cognitive complexity analysis (CLI score) | Identifying hotspots, before refactoring | claude-code, library |
 | `debug` | Hypothesis-first debugging discipline | Any test failure or bug whose cause is not immediately obvious — or a bug report with no failure text, which this skill refuses rather than guesses at | claude-code, library |
 | `discovery-framing` | Problem-before-solution discovery/framing method | Framing/validating a problem before any solution; opportunity sizing | claude-code, library |
+| `document-to-markdown` | Read .docx/.xlsx/.pptx/.epub/.msg and other formats the Read tool cannot open | You need the contents of a binary document — Word, Excel, PowerPoint, EPUB, Outlook .msg, a zip of documents — and Read returns nothing useful | claude-code, library |
 | `dream` | Reflective consolidation pass over an agent's memory directory | Pruning/merging memory files, rebuilding a memory index | claude-code, library, chat |
 | `experiment-spec` | Rigorous experiment spec — falsifiable hypothesis, quantitative acceptance, null-result protocol | Scoping a research/ML phase instead of a feature | claude-code, library |
 | `feature-spec` | Implementation-level feature spec (tighter than spec-driven-dev) | Scoping one feature inside an already-specced project | claude-code, library |

skills/document-to-markdown/SKILL.md

@@ -0,0 +1,126 @@
+---
+name: document-to-markdown
+surfaces: [claude-code, library]
+summary: "Read .docx/.xlsx/.pptx/.epub/.msg and other formats the Read tool cannot open"
+use_when: "You need the contents of a binary document — Word, Excel, PowerPoint, EPUB, Outlook .msg, a zip of documents — and Read returns nothing useful"
+description: Convert a binary document to Markdown locally with markitdown. No network, no LLM, safe for confidential material. Says when to use the docmark service instead.
+---
+
+# Document → Markdown
+
+## Overview
+
+`Read` opens PDFs, images and notebooks natively. It does **not** open `.docx`,
+`.xlsx`, `.pptx`, `.epub`, `.msg` or `.zip`. This skill converts those locally.
+
+One command, no install step, no service:
+
+```bash
+uvx --from 'markitdown[docx,pdf,pptx,xls,xlsx,outlook]' markitdown FILE > /tmp/out.md
+```
+
+First run downloads 38 packages (~10s); afterwards it is cached and instant.
+
+## When to use this
+
+You have a file on disk whose contents you need. That is the whole trigger.
+
+## When NOT to use this — use `docmark` instead
+
+Three cases, and only three:
+
+1. **A scanned PDF or an image whose content is pixels, not text.** Extracting
+   that needs a vision model. The estate's only audited path from an image to a
+   model is `docmark`, whose `sovereignty.py` constructs an LLM client *only*
+   when `DOCMARK_VISION_MODEL` matches `koala/*` or `iguana/*`, and silently
+   degrades to metadata-only otherwise. `tests/test_sovereignty.py` is the
+   load-bearing guard. Do not reach for a cloud vision model directly; that is
+   the boundary the gate exists to hold.
+2. **You are writing an in-cluster service** (something in `dispatch`,
+   `ingestion`, `cobalt-dingo`). Call `docmark` over MCP rather than bundling a
+   converter into each service. Its NetworkPolicy already admits `supervisor`
+   and `dispatch`.
+3. **The file is larger than ~25 MiB** or you want the input/output caps
+   enforced centrally.
+
+For a text-bearing document, the service returns **byte-identical output** to
+the local command — measured 2026-09-24 on the same `.docx`, tables included.
+A network hop, a bearer token and an ingress for the same bytes is not a
+trade worth making.
+
+## Confidential material
+
+**Conversion is local and involves no LLM.** `markitdown` uses an LLM client
+only to describe images; with none configured it does not call anything. No
+bytes leave the machine.
+
+That makes this safe for client material, unlike anything that routes through a
+model. Two cautions:
+
+- **Do not install `markitdown[all]`.** It pulls `az-doc-intel` and
+  `az-content-understanding` — Azure cloud document-intelligence converters.
+  They need explicit endpoint configuration to activate, but the extras list
+  above avoids having them on the path at all.
+- The output is a file like any other. If the source was confidential, so is
+  `/tmp/out.md` — and the usual rule applies: it must not reach an open-egress
+  sink (ADR-0014).
+
+## Verify the conversion, do not assume it
+
+The failure mode is **a successful exit with empty output**. A `.docx` template
+with no body content converts to zero characters and exits 0; so does a scanned
+PDF with no text layer. Both look like success.
+
+```bash
+uvx --from 'markitdown[docx,pdf,pptx,xls,xlsx,outlook]' markitdown FILE > /tmp/out.md
+wc -c /tmp/out.md
+```
+
+If the byte count is 0 or implausibly small for the document's size, the
+converter found no text layer — that is case 1 above, and it needs `docmark`
+with a vision model, not a retry.
+
+## What it converts
+
+18 converters with the extras above:
+
+```
+Audio, BingSerp, Csv, Docx, Epub, Html, Image, Ipynb, OutlookMsg, Pdf,
+PlainText, Pptx, Rss, Wikipedia, Xls, Xlsx, YouTube, Zip
+```
+
+`docmark` registers 22 — the same set plus `DocxWithOCR`, `PdfWithOCR`,
+`PptxWithOCR`, `XlsxWithOCR`. **Those four are the entire difference**, and
+they are exactly the vision path from case 1. Everything else is identical code
+running in a different place.
+
+## Reading the output
+
+Convert to a file and `Read` it, rather than piping into the transcript —
+a 200-page document produces a lot of Markdown and most of it will not be
+what you needed. Convert, then grep or read the section you want.
+
+## Provenance
+
+`docmark` ADR-0013 (`mathias/infra docs/decisions/`) owns the service; this
+skill is the local path. The split was decided in `mathias/docmark#3` on
+measurement, not preference: three of docmark's four plausible consumers are
+better served without it, and the fourth — vision under a sovereignty gate — is
+why it exists.
+
+## Escalation
+
+Local, read-only, single command. Nothing here is handed back mid-task.
+
+Stop and hand back when:
+
+- **The output is empty or near-empty.** Do not retry, and do not guess at the
+  contents. Say which file, what the byte count was, and that it needs a vision
+  path — then either use `docmark` with a local vision model, or ask. A
+  confident summary of a document you could not read is the worst possible
+  output of this skill.
+- **The document is client material and the task would send its contents
+  anywhere** — a commit message, an issue, a PR body, a cloud model. That is
+  ADR-0014's refusal, and it is not this skill's call to make.
+- **The file is encrypted or password-protected.** markitdown will fail; asking
+  for the password is a human's decision, not a retry.