fix(embeddings): reset initPromise on failure + add vector strategy path

- Reset initPromise to null on pipeline load failure so retries work
- Add vector search path for semantic strategy (was falling through to text)
- Convert vector similarity distances to scores for consistent ranking

Author: StackMemory Bot (CLI)

src/core/database/transformers-embedding-provider.ts

@@ -26,7 +26,12 @@ export class TransformersEmbeddingProvider implements EmbeddingProvider {
       const { pipeline } = await import('@xenova/transformers');
       this.pipeline = await pipeline('feature-extraction', this.modelName);
     })();
-    await this.initPromise;
+    try {
+      await this.initPromise;
+    } catch (err) {
+      this.initPromise = null;
+      throw err;
+    }
   }
 
   async embed(text: string): Promise<number[]> {

src/core/retrieval/context-retriever.ts

@@ -419,7 +419,19 @@ export class ContextRetriever {
             strategy.weights
           );
         } else {
-          // No embedding provider — fall back to text search
+          rawResults = await this.adapter.search(searchOptions);
+        }
+      } else if (strategy.searchType === 'vector') {
+        const embedding = await this.generateEmbedding(query.text);
+        if (embedding.length > 0) {
+          const vecResults = await this.adapter.searchByVector(embedding, {
+            limit: searchOptions.limit,
+          });
+          rawResults = vecResults.map((r) => ({
+            ...r,
+            score: 1 - (r.similarity || 0),
+          }));
+        } else {
           rawResults = await this.adapter.search(searchOptions);
         }
       } else {