fix: use WASM backend for Chroma embeddings to fix cross-platform issues

Chroma requires client-side embeddings — the server is storage only.
The previous commit incorrectly removed @chroma-core/default-embed.

Uses DefaultEmbeddingFunction({ wasm: true }) which forces the WASM
backend instead of native ONNX binaries. Same model (all-MiniLM-L6-v2),
same embeddings, but works on all platforms without segfaults or
ENOENT errors (#1104, #1105, #1110).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/services/sync/ChromaSync.ts

@@ -189,14 +189,20 @@ export class ChromaSync {
     }
 
     try {
-      // Let the Chroma HTTP server handle embeddings server-side.
-      // Removes dependency on @chroma-core/default-embed which requires
-      // onnxruntime + sharp native binaries that fail on many platforms (#1104, #1105, #1110).
+      // Use WASM backend to avoid native ONNX binary issues (#1104, #1105, #1110).
+      // Same model (all-MiniLM-L6-v2), same embeddings, but runs in WASM —
+      // no native binary loading, no segfaults, no ENOENT errors.
+      const { DefaultEmbeddingFunction } = await import('@chroma-core/default-embed');
+      const embeddingFunction = new DefaultEmbeddingFunction({ wasm: true });
+
       this.collection = await this.chromaClient.getOrCreateCollection({
-        name: this.collectionName
+        name: this.collectionName,
+        embeddingFunction
       });
 
-      logger.debug('CHROMA_SYNC', 'Collection ready', { collection: this.collectionName });
+      logger.debug('CHROMA_SYNC', 'Collection ready', {
+        collection: this.collectionName
+      });
     } catch (error) {
       logger.error('CHROMA_SYNC', 'Failed to get/create collection', { collection: this.collectionName }, error as Error);
       throw new Error(`Collection setup failed: ${error instanceof Error ? error.message : String(error)}`);