fix(project-init): suggest rails-patterns for Gemfile-detected repos

The ruby stack listed only tdd-workflow and verification-loop, so Rails
projects detected via Gemfile never got the framework skill suggested.

config/project-stack-mappings.json

@@ -359,6 +359,7 @@
       ],
       "rules": ["common"],
       "skills": [
+        "rails-patterns",
         "tdd-workflow",
         "verification-loop"
       ],