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>

package.json

@@ -98,6 +98,7 @@
   "dependencies": {
     "@anthropic-ai/claude-agent-sdk": "^0.1.76",
     "@modelcontextprotocol/sdk": "^1.25.1",
+    "@chroma-core/default-embed": "^0.1.9",
     "ansi-to-html": "^0.7.2",
     "chromadb": "^3.2.2",
     "dompurify": "^3.3.1",