Add archify skill (v2.14), pi-mermaid ext (v0.3.0), project-diagramming-mermaid + project-diagramming-archify skills

- skills/archify: vendored tt-a1i/archify 2.14.0 (MIT), pure Node 18+, zero deps
- extensions/pi-mermaid: renders mermaid blocks as ASCII in TUI; deps beautiful-mermaid + mermaid
- skills/project-diagramming-*: orchestration skills, per-project docs/ convention

skills/archify/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "archify",
+  "version": "2.14.0",
+  "private": true,
+  "type": "module",
+  "description": "JSON-IR diagram renderers (architecture / workflow / sequence / dataflow / lifecycle).",
+  "license": "MIT",
+  "bin": {
+    "archify": "./bin/archify.mjs"
+  },
+  "engines": {
+    "node": ">=18"
+  }
+}