refactor: remove ServiceMethods from NestJS plugin, simplify example app
Remove duplicate ServiceMethods type generation from the NestJS plugin,
keeping only ControllerMethods. Simplify the example app by inlining
controller logic and removing service layer, guards, and dead code.
Add updatePet and deletePet test coverage. Exclude NestJS example and
all .gen directories from root ESLint.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>