Document the v2.2.0 skills-based distribution

Align release notes, version metadata, installation guidance, and maintainer documentation with the canonical skills workflow.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

version.json

@@ -1,6 +1,6 @@
 {
   "name": "Plan2Code",
-  "version": "2.1.1",
+  "version": "2.2.0",
   "description": "A structured 4-step workflow methodology for AI-assisted software development",
   "keywords": [
     "ai",
@@ -17,6 +17,6 @@
     "url": "https://github.com/jparkerweb/plan2code"
   },
   "homepage": "https://github.com/jparkerweb/plan2code",
-  "releaseDate": "2026-08-12",
+  "releaseDate": "2026-08-20",
   "mode": "utility"
 }