fix: address PR #200 review issues

- Restore PROTOCOL_VERSION to a forward-compatible 2.1.0 and document wire format
- Add NULL guard to config_delete
- Add pipeline cancellation flag and cancellation-aware queue helper
- Join running threads before destroying pipeline contexts on creation failure
- Fix NULL dereference and memory leaks in manifest/chunk handling
- Fix TLS/TCP socket fd leak on connect error paths
- Add compression-level range validation (1-22)
- Close previous log file before opening a new one
- Use getline for unbounded pattern-file lines
- Fix thread-unsafe localtime() and add log level bounds check
- Fix file_load_data to clean up data on read size mismatch
- Add hard ceiling to decompression buffer growth
- Fix mkdir_r bounds check and restore glob comments
- Add send_str NULL guard and mutex-protect bandwidth limiter
- Update AGENTS.md for per-thread io_ssl contract

src/client/client_send.c

@@ -665,10 +665,11 @@ int send_files_multithreaded(Config* config) {
   if (config->use_delete)
     context->manifest = array_list_create(free);
 
-  thrd_t scanner, loader, sender;
+  thrd_t scanner, loader, sender, progress;
   bool scanner_created = false;
   bool loader_created = false;
   bool sender_created = false;
+  bool progress_created = false;
 
   scanner_created = (thrd_create(&scanner, scan_directory_multithreaded, context) == thrd_success);
   if (scanner_created)
@@ -696,8 +697,6 @@ int send_files_multithreaded(Config* config) {
     return 1;
   }
 
-  thrd_t progress;
-  bool progress_created = false;
   if (config->show_progress) {
     progress_created = (thrd_create(&progress, progress_thread_fn, context) == thrd_success);
     if (!progress_created) {
@@ -711,7 +710,7 @@ int send_files_multithreaded(Config* config) {
   thrd_join(loader, NULL);
   thrd_join(sender, &sender_result);
 
-  if (progress_created) {
+  if (config->show_progress) {
     /* Signal progress thread to exit if it hasn't already */
     mtx_lock(&context->mutex_progress);
     context->sender_done = true;

src/client/scanner.c

@@ -348,7 +348,6 @@ ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata
       ok = false;
   }
   if (ok) {
-    // cppcheck-suppress unreadVariable
     init++;
     if (cnd_init(&ps->result_not_full) != thrd_success)
       ok = false;

src/shared/multiprocessing.c

@@ -48,7 +48,6 @@ PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* que
   init++;
   if (mtx_init(&context->mutex_progress, mtx_plain) != thrd_success)
     goto fail;
-  // cppcheck-suppress unreadVariable
   init++;
   return context;
 
@@ -107,7 +106,6 @@ PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue*
   init++;
   if (cnd_init(&context->condition_not_empty) != thrd_success)
     goto fail;
-  // cppcheck-suppress unreadVariable
   init++;
   return context;