fix: harden model catalog projections

backend/src/workspaces/effective-config.ts

@@ -140,7 +140,7 @@ function buildEmbeddingConfig(rendered: Record<string, unknown>): CanonicalEmbed
   }
   const model = requireString(embeddings, "model");
   return {
-    id: `ollama/${model}`,
+    id: optionalString(embeddings, "id") ?? `ollama/${model}`,
     model,
     dimensions: requireNumber(embeddings, "dimensions"),
   };