* Replace type: ignore[attr-defined] with isinstance assertions in tests
* Fix isinstance assertions in failing tests
- Fix enum test to check for ResponseEnum instead of str
- Fix binary resource test to check for BlobResourceContents instead of TextResourceContents
- Fix Root type tests to check attributes directly instead of isinstance checks
* Fix type errors without using type: ignore
- Remove execution methods from TransformingProvider (only handles transformations)
- Add execution methods to base Provider class with default implementations
- Fix type narrowing in tests using cast() instead of type: ignore
- Fix PromptResult type handling in prompt render tests
- Fix type narrowing in middleware test for arguments and structured_content
* Use anyio as testing backend
* Remove asyncio markers
* Update streamable http tests
* Replace all subprocess tests
* Replace anyio task groups with asyncio context managers in tests
- Convert run_server_async from anyio task group pattern to asyncio.create_task with async context manager
- Remove task_group fixture from conftest
- Update all test fixtures to use async with run_server_async pattern
- Remove TaskGroup imports from all test files
- Tests now work with pytest-asyncio instead of pytest-anyio
* Update test_github_provider_integration.py
