fix(mcp-kb): add input validation, path security, and health checks

Security fixes from deep review:
- Add input validation patterns for project_id, agent_id, collection
- Add path traversal protection for source_path (reject .., null bytes)
- Add error codes (INTERNAL_ERROR) to generic exception handlers
- Handle FieldInfo objects in validation for test robustness

Performance fixes:
- Enable concurrent hybrid search with asyncio.gather

Health endpoint improvements:
- Check all dependencies (database, Redis, LLM Gateway)
- Return degraded/unhealthy status based on dependency health
- Updated tests for new health check response structure

All 139 tests pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

mcp-servers/knowledge-base/tests/test_server.py

@@ -13,10 +13,10 @@ class TestHealthCheck:
 
     @pytest.mark.asyncio
     async def test_health_check_healthy(self):
-        """Test health check when healthy."""
+        """Test health check when all dependencies are connected."""
         import server
 
-        # Create a proper async context manager mock
+        # Create a proper async context manager mock for database
         mock_conn = AsyncMock()
         mock_conn.fetchval = AsyncMock(return_value=1)
 
@@ -29,24 +29,75 @@ class TestHealthCheck:
         mock_cm.__aexit__.return_value = None
         mock_db.acquire.return_value = mock_cm
 
+        # Mock Redis
+        mock_redis = AsyncMock()
+        mock_redis.ping = AsyncMock(return_value=True)
+
+        # Mock HTTP client for LLM Gateway
+        mock_http_response = AsyncMock()
+        mock_http_response.status_code = 200
+        mock_http_client = AsyncMock()
+        mock_http_client.get = AsyncMock(return_value=mock_http_response)
+
+        # Mock embeddings with Redis and HTTP client
+        mock_embeddings = MagicMock()
+        mock_embeddings._redis = mock_redis
+        mock_embeddings._http_client = mock_http_client
+
         server._database = mock_db
+        server._embeddings = mock_embeddings
 
         result = await server.health_check()
 
         assert result["status"] == "healthy"
         assert result["service"] == "knowledge-base"
-        assert result["database"] == "connected"
+        assert result["dependencies"]["database"] == "connected"
+        assert result["dependencies"]["redis"] == "connected"
+        assert result["dependencies"]["llm_gateway"] == "connected"
 
     @pytest.mark.asyncio
     async def test_health_check_no_database(self):
-        """Test health check without database."""
+        """Test health check without database - should be unhealthy."""
         import server
 
         server._database = None
+        server._embeddings = None
 
         result = await server.health_check()
 
-        assert result["database"] == "not initialized"
+        assert result["status"] == "unhealthy"
+        assert result["dependencies"]["database"] == "not initialized"
+
+    @pytest.mark.asyncio
+    async def test_health_check_degraded(self):
+        """Test health check with database but no Redis - should be degraded."""
+        import server
+
+        # Create a proper async context manager mock for database
+        mock_conn = AsyncMock()
+        mock_conn.fetchval = AsyncMock(return_value=1)
+
+        mock_db = MagicMock()
+        mock_db._pool = MagicMock()
+
+        mock_cm = AsyncMock()
+        mock_cm.__aenter__.return_value = mock_conn
+        mock_cm.__aexit__.return_value = None
+        mock_db.acquire.return_value = mock_cm
+
+        # Mock embeddings without Redis
+        mock_embeddings = MagicMock()
+        mock_embeddings._redis = None
+        mock_embeddings._http_client = None
+
+        server._database = mock_db
+        server._embeddings = mock_embeddings
+
+        result = await server.health_check()
+
+        assert result["status"] == "degraded"
+        assert result["dependencies"]["database"] == "connected"
+        assert result["dependencies"]["redis"] == "not initialized"
 
 
 class TestSearchKnowledgeTool: