docs: clarify pytest-asyncio is an optional test dep in CLAUDE.md

Without `pip install -e '.[test]'`, pytest silently skips 4 async tests
in test_sdk.py (all marked @pytest.mark.asyncio). Clarify the two-step
install so new contributors don't waste time debugging silent test failures.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CLAUDE.md

@@ -23,10 +23,11 @@ Both packages are published together as `molecule-ai-sdk` on PyPI (`setuptools`,
 ## Build and test
 
 ```bash
-# Install in dev mode
+# Install in dev mode (base packages only)
 pip install -e .
 
-# Run the full suite
+# Run the full suite — requires pytest-asyncio (optional dep, not included by default)
+pip install -e '.[test]'
 pytest
 
 # Run only molecule_agent tests (remote-agent client)