WP-0005: wave-2 queue, promote ihp-railiance-probe, smaller restore chunks

Document tier-2/3 promotion queue; note ihp-railiance-probe tier-1 promotion;
align restore drill chunk size with backup tooling.

tools/forgejo-restore-drill.sh

@@ -26,7 +26,7 @@ copy_backup_to_pod() {
   step "Chunked copy (${size} bytes) to pod"
   chunk_dir="$(mktemp -d)"
   trap 'rm -rf "${chunk_dir}"' RETURN
-  split -b 48m -a 3 "${src}" "${chunk_dir}/part-"
+  split -b 16m -a 3 "${src}" "${chunk_dir}/part-"
   for part in "${chunk_dir}"/part-*; do
     kubectl cp "${part}" "${dest_ns}/${dest_pod}:/backup/$(basename "${part}")" -c "${container}"
   done