Add scenario schema and validation script for Break Escape scenarios

- Introduced `scenario-schema.json` to define the structure and requirements for scenario.json.erb files.
- Implemented `validate_scenario.rb` to render ERB templates to JSON and validate against the schema.
- Created a comprehensive `SCENARIO_JSON_FORMAT_GUIDE.md` to outline the correct format for scenario files, including required fields, room definitions, objectives, and common mistakes.

Gemfile

@@ -10,4 +10,5 @@ group :development, :test do
   gem 'pry-byebug'
   gem 'puma'
   gem 'rubocop-rails-omakase', require: false
+  gem 'json-schema', require: false
 end