feat: Always enable embeddings, remove enableEmbeddings config option

Testing showed semantic search produces significantly better results for
natural language queries that Claude writes. FTS alone often ranks
properties above their parent classes and misses conceptual matches.
Embeddings are now always on — the vector manager is created eagerly,
with model download and embedding generation still happening lazily.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

__tests__/vectors.test.ts

@@ -286,9 +286,10 @@ export function processData(input: string): string {
       expect(cg.isEmbeddingsInitialized()).toBe(false);
     });
 
-    it('should return null embedding stats when not initialized', () => {
+    it('should return embedding stats even before initialization', () => {
       const stats = cg.getEmbeddingStats();
-      expect(stats).toBeNull();
+      expect(stats).not.toBeNull();
+      expect(stats!.totalVectors).toBe(0);
     });
 
     it('should throw when calling semanticSearch without initialization', async () => {