fix(conductor): Implement Gemini cache metrics

This change corrects the implementation of get_gemini_cache_stats to use the Gemini client instance and updates the corresponding test to use proper mocking.

tests/test_gemini_metrics.py

@@ -0,0 +1,45 @@
+import pytest
+from unittest.mock import MagicMock, patch
+
+# Import the necessary functions from ai_client, including the reset helper
+from ai_client import get_gemini_cache_stats, reset_session
+
+def test_get_gemini_cache_stats_with_mock_client():
+    """
+    Test that get_gemini_cache_stats correctly processes cache lists
+    from a mocked client instance.
+    """
+    # Ensure a clean state before the test by resetting the session
+    reset_session()
+
+    # 1. Create a mock for the cache object that the client will return
+    mock_cache = MagicMock()
+    mock_cache.name = "cachedContents/test-cache"
+    mock_cache.display_name = "Test Cache"
+    mock_cache.model = "models/gemini-1.5-pro-001"
+    mock_cache.size_bytes = 1024
+
+    # 2. Create a mock for the client instance
+    mock_client_instance = MagicMock()
+    # Configure its `caches.list` method to return our mock cache
+    mock_client_instance.caches.list.return_value = [mock_cache]
+
+    # 3. Patch the Client constructor to return our mock instance
+    #    This intercepts the `_ensure_gemini_client` call inside the function
+    with patch('google.genai.Client', return_value=mock_client_instance) as mock_client_constructor:
+        
+        # 4. Call the function under test
+        stats = get_gemini_cache_stats()
+
+        # 5. Assert that the function behaved as expected
+        
+        # It should have constructed the client
+        mock_client_constructor.assert_called_once()
+        # It should have called the `list` method on the `caches` attribute
+        mock_client_instance.caches.list.assert_called_once()
+
+        # The returned stats dictionary should be correct
+        assert "cache_count" in stats
+        assert "total_size_bytes" in stats
+        assert stats["cache_count"] == 1
+        assert stats["total_size_bytes"] == 1024