fix: Add noqa comment to suppress ruff F401 warning for anthropic import

The anthropic import is only used to check availability, not actually used in
code. Added # noqa: F401 comment to suppress 'imported but unused' warning.

Fixes GitHub Actions ruff linting failure.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/test_issue_219_e2e.py

@@ -24,7 +24,7 @@ sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "src"))
 
 # Check if anthropic is available
 try:
-    import anthropic
+    import anthropic  # noqa: F401
     ANTHROPIC_AVAILABLE = True
 except ImportError:
     ANTHROPIC_AVAILABLE = False