feat: add mmd-it marketplace + mmd-workspace plugin (4 MMD skills)

Org-wide Claude Desktop plugin marketplace for MMD Group IT. Adds the
mmd-it marketplace manifest and the mmd-workspace plugin
(installationPreference: required) carrying four skills grounded in
real MMD material: mmd-document-style, mmd-email-style,
mmd-it-support, mmd-data-handling. Public repo, no secrets — MCP
credentials are delivered separately via managedMcpServers.

plugins/mmd-workspace/skills/mmd-document-style/SKILL.md

@@ -0,0 +1,58 @@
+---
+name: mmd-document-style
+description: Use when writing, formatting, or reviewing any MMD / MMD Steel Group IT document meant to look official — memos, policies, status reports, audits, process docs, or anything going out under the MMD or Baobab name as a Word or PDF file. Triggers on "MMD format", "MMD branded", "MMD Word doc", "MMD report", "baobab-red", "house style", or "make this look like an MMD document".
+---
+
+# MMD document house style
+
+MMD Steel Group IT documents follow one house style. The goal is a document that reads as
+official, dense, and quick to scan on a page — not a slide deck blown up to paper size.
+
+## Type and layout
+
+- **Body text: 8-8.5pt.** MMD documents run small and dense. Do not default to 11-12pt body
+  copy — that is web-writing habit, not this house style.
+- **Title: 12pt maximum, bold, ink-black.** Titles are not hero headlines. No title larger than
+  12pt, ever, on an MMD document.
+- Prefer a serif or a clean UI serif (Aptos is the standard MMD body font) over a display
+  sans for body copy — it reads better dense and small.
+- Subtitle (if any): italic, in the accent red, smaller than the title.
+- A short grey metadata block under the title works well: Prepared by / for, date, status —
+  then a red rule dividing it from the body.
+
+## Color
+
+- Accent: baobab red, `#8B1A1A`. Use it sparingly — section numbers, the title-divider rule,
+  small accents. It is not a background color and not a body-text color.
+- Ink: `#1A1A1A` for headings and emphasis. Body: `#333333`. Supporting greys: `#666666` /
+  `#999999`.
+- Never invent a new palette or reach for a different red. If baobab red looks wrong for a
+  specific document, that is a house-style question to raise, not something to improvise
+  around locally.
+
+## Density and content rules
+
+- No dashboards, no oversized stat cards, no decorative whitespace. A working MMD document is
+  a working surface, not a poster.
+- Every table should be tight: minimal row padding, real data, no placeholder or "illustrative"
+  rows presented as if real.
+- Cut narration about the document itself ("this report was prepared using...", "how this
+  document is organized"). State the content; do not explain the act of writing it.
+- Footer convention: `MMD Steel Group IT | CONFIDENTIAL | Your partner in steel`.
+
+## Producing the file
+
+If a local MMD document-rendering pipeline is available in the working environment (Markdown
+in, branded `.docx`/`.pdf` out, built on the real MMD policy-document template with the logo
+header and footer baked in), prefer it over hand-building a Word document from scratch — it
+already encodes the header, footer, and color/type rules above. If no such pipeline is
+available, apply every rule in this skill by hand: 8-8.5pt body, <=12pt title, baobab red as a
+sparing accent only, dense layout, real content only.
+
+## What NOT to do
+
+- Do not use a different brand red, a different footer line, or a heavier/larger title "for
+  emphasis" — house style is fixed centrally, not per document.
+- Do not pad a short document with restated headings, a table of contents for a two-page memo,
+  or decorative section dividers.
+- Do not present sample/placeholder figures as if they were real reported numbers.