Claude Code plugin manifest and marketplace install line

.claude-plugin/plugin.json makes the repository a single-skill plugin
(SKILL.md stays at the root). README shows the marketplace route next
to npx skills add; one route per machine.

.claude-plugin/plugin.json

@@ -0,0 +1,10 @@
+{
+  "name": "archify-vscode-ext",
+  "version": "1.0.0",
+  "description": "Author, validate, render and manage Archify diagrams and models (registries, decisions, C4 folders) as read by the Archify Diagram Viewer VS Code extension.",
+  "author": { "name": "Root At Skic" },
+  "license": "MIT",
+  "homepage": "https://gitea.lego-cloud.eu/vscode-extensions-skills/archify-vscode-ext",
+  "repository": "https://gitea.lego-cloud.eu/vscode-extensions-skills/archify-vscode-ext.git",
+  "keywords": ["archify", "architecture", "c4", "diagrams", "skills"]
+}

README.md

@@ -11,7 +11,14 @@ npx skills add https://gitea.lego-cloud.eu/vscode-extensions-skills/archify-vsco
 npx skills update --global
 ```
 
-Or clone the repository into your agent's skills folder (`~/.claude/skills`, `~/.agents/skills`) and `git pull` to update. Keep one copy per machine: a skill installed twice is offered to the agent twice. The bundled Archify version is printed by every `task model:validate` run (`archify: 3.0.1`), so a stale copy is easy to spot.
+In Claude Code, the same skill is also a plugin of the `root-at-skic` marketplace, with background updates once you switch them on for the marketplace:
+
+```
+/plugin marketplace add https://gitea.lego-cloud.eu/global-skills/marketplace.git
+/plugin install archify-vscode-ext@root-at-skic
+```
+
+Or clone the repository into your agent's skills folder (`~/.claude/skills`, `~/.agents/skills`) and `git pull` to update. Pick one route per machine: a skill installed twice is offered to the agent twice. The bundled Archify version is printed by every `task model:validate` run (`archify: 3.0.1`), so a stale copy is easy to spot.
 
 Quick start: