Implementation of a Test Compatibility Kit for runtimes

[brunoborges]

This pull request introduces the Prompty Test Compatibility Kit (TCK), including a new GitHub Actions workflow, and test templates and expected outputs. The most important changes are grouped into workflow improvements, runtime support enhancements, and test template updates.

These changes collectively implement the TCK's functionality, compatibility across runtime implementations.

[sethjuarez]

Thank you for your contribution! We've migrated Prompty to v2 on main — the codebase has been significantly restructured with AgentSchema-based types, scoped @prompty/* npm packages, and new runtimes.

The v1 code is now preserved on the v1 branch for maintenance. If your change is still relevant for v1, please re-open against the v1 branch. For v2 contributions, please open a new PR against main.

Apologies for any inconvenience, and thanks for your patience!