Best practice for smoke testing generated code after emitter move to typespec-azure

## Context

When `@azure-tools/typespec-ts` lived in [Azure/autorest.typescript](https://github.com/Azure/autorest.typescript), we had a sibling package `typespec-test` that served as a **smoke test**: it ran the emitter against a large suite of TypeSpec specs and committed the full generated TypeScript output into the repo. This gave us several practical benefits during day-to-day development:

- **Diffable generated code** — any emitter change produced a visible diff in PRs, making regressions and unintended changes obvious at review time.
- **Easy local debugging** — contributors could open the generated client code directly, set breakpoints, inspect output, and iterate on the emitter quickly.
- **End-to-end coverage** — caught build/compile/format issues in generated code that unit tests and Spector tests don't surface.

After the emitter moved to [Azure/typespec-azure](https://github.com/Azure/typespec-azure/tree/main/packages/typespec-ts), `typespec-test` was **not** moved along with it because of the size of the committed generated code. As a result, we've lost the convenient "see the diff, debug the output" workflow in the new repo.

## Discussion

I'd like to hear from other language emitter owners (Python, Java, Go, etc.) on how they handle this:

- Do you keep a smoke-test-style fixture repo with committed generated code? Where does it live?
- If not, how do you review the impact of an emitter change on real-world output before merging?
- How do contributors locally debug generated code against an in-development emitter?
- Are there shared tools or conventions in `typespec-azure` we could adopt instead of each language reinventing one?

## Goal

Agree on a best practice for TypeScript (and potentially other languages) so that:

1. PR reviewers can still see the impact of emitter changes on generated code.
2. Contributors retain a fast inner-loop for debugging generated output.
3. We don't bloat the main repo with megabytes of generated code.