rsync flags: -a, -n, -p, --exclude, --delete

Feature changes across 15 files:

- -a/--archive: enables -c -m -M (no -s, which slows transfers)
- -n/--dry-run: scan + print without connecting or transferring
- -p <port>: custom SSH port (passed as -p to ssh via execvp)
- --exclude <pattern>: glob-based filename filtering in scanner
- --delete: sender collects file manifest; receiver deletes unlisted files

Protocol: added STATUS_MANIFEST, use_delete field in Config wire format.
New utilities: glob_match(), delete_extras() with recursive directory walk.
Scanner: accepts exclude patterns; skips matching entries.
SSH transport: switched from execlp to execvp for dynamic port arg.
Server + multiprocessing: handle STATUS_MANIFEST in both single and
multithreaded receive paths.

Builds clean, all 7 tests pass.

src/shared/multiprocessing.c

@@ -1,4 +1,5 @@
 #include "multiprocessing.h"
+#include "array_list.h"
 #include "chunk.h"
 #include "compression.h"
 #include "config.h"
@@ -36,6 +37,11 @@ PipelineContextSender *pipeline_context_sender_create(Config *config,
 }
 
 void pipeline_context_sender_destroy(PipelineContextSender *context) {
+  if (context->manifest) {
+    for (int i = 0; i < context->manifest->size; i++)
+      free(context->manifest->items[i]);
+    array_list_delete(context->manifest);
+  }
   config_delete(context->config);
   queue_destroy(context->queue_scanner);
   queue_destroy(context->queue_loader);
@@ -119,6 +125,17 @@ int receive_thread(void *pipeline_context) {
     }
     status = receive_status(file_descriptor);
   }
+  if (status == STATUS_MANIFEST) {
+    int count = receive_int(file_descriptor);
+    ArrayList *manifest = array_list_create(free);
+    for (int i = 0; i < count; i++)
+      array_list_add(manifest, receive_str(file_descriptor));
+    delete_extras(context->config->receive_root_directory, manifest);
+    for (int i = 0; i < manifest->size; i++)
+      free(manifest->items[i]);
+    array_list_delete(manifest);
+    status = receive_status(file_descriptor);
+  }
   mtx_lock(&context->mutex);
   context->receiver_done = true;
   cnd_signal(&context->condition_not_empty);