feat(skills): Add dhh-rails-style skill for 37signals Rails conventions

Router-pattern skill with sectioned references:
- controllers.md: REST mapping, concerns, Turbo, API patterns
- models.md: Concerns, state records, callbacks, scopes
- frontend.md: Turbo, Stimulus, CSS architecture
- architecture.md: Routing, auth, jobs, caching, config
- gems.md: What they use vs avoid, decision framework

Based on analysis of Fizzy (Campfire) codebase.

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

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

.claude-plugin/marketplace.json

@@ -11,8 +11,8 @@
   "plugins": [
     {
       "name": "compound-engineering",
-      "description": "AI-powered development tools that get smarter with every use. Make each unit of engineering work easier than the last. Includes 25 specialized agents, 19 commands, and 12 skills.",
-      "version": "2.10.0",
+      "description": "AI-powered development tools that get smarter with every use. Make each unit of engineering work easier than the last. Includes 27 specialized agents, 17 commands, and 13 skills.",
+      "version": "2.13.0",
       "author": {
         "name": "Kieran Klaassen",
         "url": "https://github.com/kieranklaassen",