chore(InMemoryEmbeddingSearchIndex): replace custom concurrent set with ConcurrentHashMap.newKeySet #200

This change improves the performance and memory usage by utilizing the built-in `ConcurrentHashMap.newKeySet()` for the `uncheckedIds` set, which provides a more efficient concurrent implementation.

Author: phodal

src/main/kotlin/cc/unitmesh/devti/embedding/InMemoryEmbeddingSearchIndex.kt

@@ -27,7 +27,7 @@ import kotlin.to
  */
 class InMemoryEmbeddingSearchIndex(root: Path, limit: Int? = null) : EmbeddingSearchIndex {
     private var idToEmbedding: MutableMap<String, FloatArray> = CollectionFactory.createSmallMemoryFootprintMap()
-    private val uncheckedIds: MutableSet<String> = ConcurrentCollectionFactory.createConcurrentSet()
+    private val uncheckedIds: MutableSet<String> = java.util.concurrent.ConcurrentHashMap.newKeySet()
     private val lock = ReentrantReadWriteLock()
 
     private val fileManager = LocalEmbeddingIndexFileManager(root)