test: Skip tests requiring optional dependencies

- Skip test_benchmark.py if psutil not installed
- Skip test_embedding.py if numpy not installed
- Skip test_embedding_pipeline.py if numpy not installed
- Uses pytest.importorskip() for clean dependency handling
- Fixes CI test collection errors for optional features

tests/test_embedding.py

@@ -7,6 +7,9 @@ import tempfile
 from pathlib import Path
 from unittest.mock import patch
 
+# Skip all tests if numpy is not installed
+pytest.importorskip("numpy")
+
 from skill_seekers.embedding.models import (
     EmbeddingRequest,
     BatchEmbeddingRequest,