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>

plugins/compound-engineering/CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to the compound-engineering plugin will be documented in thi
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.13.0] - 2025-12-15
+
+### Added
+
+- **`dhh-rails-style` skill** - Write Ruby and Rails code in DHH's distinctive 37signals style. Router-pattern skill with sectioned references for controllers, models, frontend, architecture, and gems. Embodies REST purity, fat models, thin controllers, Current attributes, Hotwire patterns, and the "clarity over cleverness" philosophy. Based on analysis of Fizzy (Campfire) codebase.
+
 ## [2.12.0] - 2025-12-15
 
 ### Added