fix: address all remaining review warnings and style issues

- config.h: bump PROTOCOL_VERSION from "1.2.0" to "1.3.0" (WARNING-1)
- client_cli.c: fix realloc leak on exclude/include patterns (WARNING-2)
- file.c: document sendfile fallback as safety net only (WARNING-4)
- metadata.c: add warning log for utimensat failure (WARNING-5/STYLE-1)
- utils.c: fix is_dir_in_manifest false prefix match (WARNING-1)
- utils.c: fix double rmdir on recursive collapse, add errno.h (WARNING-2)
- client_send.c: guard unchecked send calls for manifest/finished (WARNING-3)
- client_send.c: send STATUS_NEXT on rc==2 without delta (WARNING-4)

src/shared/file.c

@@ -448,6 +448,11 @@ bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int
                         bool send_path) {
   // sendfile is incompatible with compression (kernel zero-copy).
   // If compression is requested, fall back to the regular send path.
+  // NOTE: This is a safety net only — callers must ensure compression_level == 0
+  // before calling file_send_sendfile. The fallback to file_send_single_calls
+  // preserves the send_path contract, but callers should not rely on it for
+  // correctness (the --sendfile flag is validated to be mutually exclusive with
+  // -c/--compress at the CLI layer).
   if (compression_level > 0)
     return file_send_single_calls(file, file_descriptor, use_metadata, compression_level,
                                   send_path);