refactor(scanner,send): embed scanner options; unify stats and config ownership

src/shared/multiprocessing.c

@@ -179,6 +179,9 @@ bool pipeline_context_sender_enqueue_chunk(PipelineContextSender* context, Chunk
 }
 
 void pipeline_context_sender_destroy(PipelineContextSender* context) {
+  /* `config` is borrowed: the caller retains ownership and frees it after the
+     pipeline has been destroyed (the worker threads are already joined, so no
+     config access can outlive this call). */
   if (context->manifest) {
     array_list_delete(context->manifest);
   }
@@ -192,7 +195,6 @@ void pipeline_context_sender_destroy(PipelineContextSender* context) {
     array_list_delete(context->dir_entries);
   if (context->dir_entries_mutex_init)
     mtx_destroy(&context->dir_entries_mutex);
-  config_delete(context->config);
   queue_destroy(context->queue_scanner);
   queue_destroy(context->queue_loader);
   mtx_destroy(&context->mutex_scanner);

src/shared/multiprocessing.h

@@ -120,6 +120,8 @@ typedef struct PipelineContextReceiver {
   DirTimeList dir_times;
 } PipelineContextReceiver;
 
+/* `config` is borrowed and must outlive the context: destroy does NOT free it,
+   so the caller owns it and frees it with config_delete() afterwards. */
 PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* queue_scanner,
                                                       Queue* queue_loader);
 void pipeline_context_sender_destroy(PipelineContextSender* context);