Add event loop yields so SSE events flush during search

Without yields, the async operations block the event loop and
SSE events pile up unsent until the entire search completes.
Adding setTimeout(0) yields after start and store_complete events
lets Node.js flush the write buffer to the client.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server/scraper/engine.ts

@@ -161,6 +161,9 @@ export async function searchStreaming(
     stores: stores.map((s) => ({ id: s.id, name: s.name, renderJs: !!s.render_js })),
   });
 
+  // Yield to event loop so the SSE start event flushes to client
+  await new Promise((r) => setTimeout(r, 0));
+
   const limit = pLimit(MAX_CONCURRENCY);
   const errors: SearchResult['meta']['errors'] = [];
   let totalResults = 0;
@@ -193,6 +196,9 @@ export async function searchStreaming(
           resultCount: products.length,
           duration,
         });
+
+        // Yield so SSE event flushes to client
+        await new Promise((r) => setTimeout(r, 0));
       } catch (err) {
         const duration = Date.now() - storeStart;
         const errorMessage = err instanceof Error ? err.message : String(err);