Add compression statistics output

- Track compressed files count
- Track skipped files count
- Track compressed bytes
- Display compression ratio and savings in sync complete message

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

src/client.c

@@ -198,6 +198,9 @@ typedef struct {
 
 static atomic_uint_fast64_t g_bytes_sent = 0;
 static atomic_uint_fast32_t g_files_sent = 0;
+static atomic_uint_fast64_t g_bytes_compressed = 0;
+static atomic_uint_fast32_t g_files_compressed = 0;
+static atomic_uint_fast32_t g_files_skipped = 0;
 
 // ─── UDP session setup (called once per worker if -u) ─────────────────────
 
@@ -841,6 +844,16 @@ static int send_batch_files(sync_ctx_t *ctx, file_task_t **tasks, int count) {
 
         close(fds[i]);
         atomic_fetch_add(&g_bytes_sent, (uint64_t)stats[i].st_size);
+        
+        // Update compression statistics
+        if (meta.compress == COMPRESS_LZ4) {
+            atomic_fetch_add(&g_files_compressed, 1);
+            atomic_fetch_add(&g_bytes_compressed, (uint64_t)meta.compressed_size);
+        } else if (use_sendfile) {
+            // File was skipped for compression (already compressed or too small)
+            atomic_fetch_add(&g_files_skipped, 1);
+        }
+        
         // Note: data_to_send points to batch-level buffers (file_buf/comp_buf), NOT freed per-file
         printf("[thread] Sent (pipelined+%s): %s\n", meta.compress == COMPRESS_LZ4 ? "compress" : "buffered", tasks[i]->rel_path);
     }
@@ -1221,10 +1234,24 @@ int main(int argc, char *argv[]) {
 
     uint64_t total_bytes = atomic_load(&g_bytes_sent);
     uint32_t total_files = atomic_load(&g_files_sent);
+    uint32_t files_compressed = atomic_load(&g_files_compressed);
+    uint32_t files_skipped = atomic_load(&g_files_skipped);
+    uint64_t bytes_compressed = atomic_load(&g_bytes_compressed);
     double   throughput  = (total_bytes / 1048576.0) / (elapsed_ms / 1000.0);
 
     printf("\n=== Sync complete: %u files, %lu bytes, %.1f ms, %.2f MB/s ===\n",
            total_files, (unsigned long)total_bytes, elapsed_ms, throughput);
+    
+    // Print compression statistics if compression was enabled
+    if (use_compress && total_files > 0) {
+        if (files_compressed > 0 || files_skipped > 0) {
+            double compress_ratio = (bytes_compressed > 0) ? 
+                (double)(total_bytes - bytes_compressed) / (double)bytes_compressed : 0;
+            printf("Compression stats: %u compressed, %u skipped (%.1f%% savings)\n",
+                   files_compressed, files_skipped, compress_ratio * 100);
+        }
+    }
+    
     /* Machine-readable line for benchmark.sh to parse */
     printf("BENCH: connections=%d bytes=%lu ms=%.1f throughput_mbs=%.2f\n",
            nconn, (unsigned long)total_bytes, elapsed_ms, throughput);