feat(knowledge-base): implement Knowledge Base MCP Server (#57)

Implements RAG capabilities with pgvector for semantic search:

- Intelligent chunking strategies (code-aware, markdown-aware, text)
- Semantic search with vector similarity (HNSW index)
- Keyword search with PostgreSQL full-text search
- Hybrid search using Reciprocal Rank Fusion (RRF)
- Redis caching for embeddings
- Collection management (ingest, search, delete, stats)
- FastMCP tools: search_knowledge, ingest_content, delete_content,
  list_collections, get_collection_stats, update_document

Testing:
- 128 comprehensive tests covering all components
- 58% code coverage (database integration tests use mocks)
- Passes ruff linting and mypy type checking

🤖 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_config.py

@@ -0,0 +1,104 @@
+"""Tests for configuration module."""
+
+import os
+
+
+class TestSettings:
+    """Tests for Settings class."""
+
+    def test_default_values(self, settings):
+        """Test default configuration values."""
+        assert settings.port == 8002
+        assert settings.embedding_dimension == 1536
+        assert settings.code_chunk_size == 500
+        assert settings.search_default_limit == 10
+
+    def test_env_prefix(self):
+        """Test environment variable prefix."""
+        from config import Settings, reset_settings
+
+        reset_settings()
+        os.environ["KB_PORT"] = "9999"
+
+        settings = Settings()
+        assert settings.port == 9999
+
+        # Cleanup
+        del os.environ["KB_PORT"]
+        reset_settings()
+
+    def test_embedding_settings(self, settings):
+        """Test embedding-related settings."""
+        assert settings.embedding_model == "text-embedding-3-large"
+        assert settings.embedding_batch_size == 100
+        assert settings.embedding_cache_ttl == 86400
+
+    def test_chunking_settings(self, settings):
+        """Test chunking-related settings."""
+        assert settings.code_chunk_size == 500
+        assert settings.code_chunk_overlap == 50
+        assert settings.markdown_chunk_size == 800
+        assert settings.markdown_chunk_overlap == 100
+        assert settings.text_chunk_size == 400
+        assert settings.text_chunk_overlap == 50
+
+    def test_search_settings(self, settings):
+        """Test search-related settings."""
+        assert settings.search_default_limit == 10
+        assert settings.search_max_limit == 100
+        assert settings.semantic_threshold == 0.7
+        assert settings.hybrid_semantic_weight == 0.7
+        assert settings.hybrid_keyword_weight == 0.3
+
+
+class TestGetSettings:
+    """Tests for get_settings function."""
+
+    def test_returns_singleton(self):
+        """Test that get_settings returns singleton."""
+        from config import get_settings, reset_settings
+
+        reset_settings()
+        settings1 = get_settings()
+        settings2 = get_settings()
+        assert settings1 is settings2
+
+    def test_reset_creates_new_instance(self):
+        """Test that reset_settings clears the singleton."""
+        from config import get_settings, reset_settings
+
+        settings1 = get_settings()
+        reset_settings()
+        settings2 = get_settings()
+        assert settings1 is not settings2
+
+
+class TestIsTestMode:
+    """Tests for is_test_mode function."""
+
+    def test_returns_true_when_set(self):
+        """Test returns True when IS_TEST is set."""
+        from config import is_test_mode
+
+        old_value = os.environ.get("IS_TEST")
+        os.environ["IS_TEST"] = "true"
+
+        assert is_test_mode() is True
+
+        if old_value:
+            os.environ["IS_TEST"] = old_value
+        else:
+            del os.environ["IS_TEST"]
+
+    def test_returns_false_when_not_set(self):
+        """Test returns False when IS_TEST is not set."""
+        from config import is_test_mode
+
+        old_value = os.environ.get("IS_TEST")
+        if old_value:
+            del os.environ["IS_TEST"]
+
+        assert is_test_mode() is False
+
+        if old_value:
+            os.environ["IS_TEST"] = old_value