Checkpoint the party/runtime stack before share-program and malicious-mode work.

Ship the TLS mesh, composer, Beaver/Yao/leaf MPC, prep/online paths, apps, and docs so the tree is pushable before elevating share_expr, security_mode, and prep resume.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/dpf/protocol_roles.hpp

@@ -0,0 +1,68 @@
+/// @file dpf/protocol_roles.hpp
+/// @brief Thin helpers for dealer, preprocess, and online roles.
+/// @details Three modes:
+///          - **Dealer** — sample prep and write per-party views (files or streams).
+///          - **Preprocess** — exchange dealer output over the network (e.g. mux TCP).
+///          - **Online** — parties read prep and run interactive rounds on peer streams.
+#ifndef LIBDPF_INCLUDE_DPF_PROTOCOL_ROLES_HPP__
+#define LIBDPF_INCLUDE_DPF_PROTOCOL_ROLES_HPP__
+
+#include <cstddef>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "hedley/hedley.h"
+
+#include "dpf/net/channel.hpp"
+#include "dpf/net/stream_array.hpp"
+#include "dpf/prep_source.hpp"
+
+namespace dpf
+{
+namespace roles
+{
+
+/// @brief Dealer mode: write `basename-p0`, `basename-p1` prep blobs.
+inline void dealer_write_files(const std::string & basename,
+    const prep::demand & d)
+{
+    auto views = prep::deal_views(d);
+    prep::write_file(basename + "-p0", views.first);
+    prep::write_file(basename + "-p1", views.second);
+}
+
+/// @brief Preprocess mode: party 0 deals into mux streams; party 1 receives.
+/// @details Party 0 writes its view locally and ships party 1's view on stream 0.
+inline std::vector<std::uint8_t> preprocess_from_dealer_mux(net::channel & ch,
+    unsigned party, const prep::demand & d, net::stream_array & local_out)
+{
+    if (local_out.size() < 1)
+        throw std::invalid_argument("preprocess_from_dealer_mux: need stream 0");
+    if (party == 0)
+    {
+        auto views = prep::deal_views(d);
+        local_out.write(0, views.first.data(), views.first.size());
+        local_out.flush(0);
+        ch.send_vec(views.second, net::msg::beaver_tape);
+        return std::move(views.first);
+    }
+    auto got = ch.recv_vec<std::uint8_t>(net::msg::beaver_tape);
+    local_out.write(0, got.data(), got.size());
+    local_out.flush(0);
+    return got;
+}
+
+/// @brief Online mode: open prep cursors from dealer files (`basename-p0/p1`).
+HEDLEY_WARN_UNUSED_RESULT
+inline std::pair<prep::cursor, prep::cursor> online_open_file_array(
+    const std::string & basename)
+{
+    return {prep::cursor(prep::read_file(basename + "-p0")),
+        prep::cursor(prep::read_file(basename + "-p1"))};
+}
+
+}  // namespace roles
+}  // namespace dpf
+
+#endif