Only flush JSONL on import if there were actual changes

Avoid unnecessary I/O when import has no updates

cmd/bd/import.go

@@ -178,7 +178,10 @@ Behavior:
 
 		// Flush immediately after import (no debounce) to ensure daemon sees changes
 		// Without this, daemon FileWatcher won't detect the import for up to 30s
-		flushToJSONL()
+		// Only flush if there were actual changes to avoid unnecessary I/O
+		if result.Created > 0 || result.Updated > 0 || len(result.IDMapping) > 0 {
+			flushToJSONL()
+		}
 
 		// Print summary
 		fmt.Fprintf(os.Stderr, "Import complete: %d created, %d updated", result.Created, result.Updated)