[2.16.0] Consolidate DHH styles and add /feature-video command

- Merge dhh-ruby-style into dhh-rails-style for comprehensive Rails conventions
- Add testing.md reference covering Rails testing patterns
- Add /feature-video command for recording PR demo videos
- Update docs and component counts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/compound-engineering/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "compound-engineering",
   "version": "2.20.0",
-  "description": "AI-powered development tools. 27 agents, 20 commands, 13 skills, 2 MCP servers for code review, research, design, and workflow automation.",
+  "description": "AI-powered development tools. 27 agents, 20 commands, 12 skills, 2 MCP servers for code review, research, design, and workflow automation.",
   "author": {
     "name": "Kieran Klaassen",
     "email": "kieran@every.to",