## Summary
- add a public `defineStackConfig` helper and `StackConfig` type for
nested config authoring
- emit helper-based nested config files from the CLI and local emulator
- update type coverage and e2e expectations for the new `stack.config`
format
## Testing
- pnpm --filter ./packages/stack-shared typecheck
- pnpm --filter ./packages/stack-cli typecheck
- pnpm --filter ./apps/backend typecheck
- pnpm --filter ./apps/e2e typecheck
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Type-safe configuration API with compile-time validation
* New config rendering utility for producing typed config files
* Public local-emulator settings and a public helper to detect emulator
mode
* Added --overwrite flag for config pull
* **Improvements**
* Stronger validation and clearer errors for invalid or conflicting
config shapes
* Config output now includes explicit TypeScript typing
* **Tests**
* Added and strengthened tests for config authoring, rendering, CLI
behavior, and emulator flows
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
