Implement SEP-1730: Conformance testing

[movetz]

The context:

• SEP-1730: SDKs Tiering System
• SEP 1730: SDK tiers definition
• https://github.com/modelcontextprotocol/conformance
• https://github.com/modelcontextprotocol/conformance/blob/main/SDK_INTEGRATION.md
• Discord message

Outcome:

• The conformance test suite has been added to the SDK repository.
• The suite is available for local runs and CI
• The suite will be used as an alignment reference for future updates; passing all tests is not the goal here