Initial commit: Naut-Torrent — from-scratch 10 GbE BitTorrent client

A maintainable, extensible BitTorrent client (C11, Linux/io_uring) targeting
10 GbE saturation. All torrent functionality is built from scratch; liburing
is the only linked third-party dependency on the data path.

Implements Phases 1-7 of the roadmap:
- core: page-aligned buffer pool, MPMC/Treiber queues, bitfields, worker pool
- crypto: SHA-1/256 (SHA-NI + scalar), Merkle (BEP-52), RC4 (MSE)
- bencode/metainfo: zero-copy parser, v1/v2/hybrid .torrent + magnet
- peer: sans-IO wire codec, MSE/PE handshake state machine, BEP-10, ut_metadata, PEX
- piece/storage: block-level multi-peer engine, rarest-first + endgame,
  per-file completion events + single-file relocate (move-as-you-finish)
- tracker/dht: HTTP + UDP (BEP-15) trackers, BEP-5 KRPC iterative lookup
- platform: io_uring reactor (SQPOLL, registered buffers, SEND_ZC)
- surface: versioned RPC, native plugin ABI, sandboxed Lua scripting, nautd/nautctl

Verified against libtorrent (single/multi/hybrid, MSE, magnet-via-DHT, swarm);
unit + interop tests green; ASan/UBSan/TSan clean. Scripting reference in
docs/scripting.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

include/naut/plugin.h

@@ -0,0 +1,25 @@
+/* plugin.h - native plugin loader and registered backend inventory. */
+#ifndef NAUT_PLUGIN_HOST_H
+#define NAUT_PLUGIN_HOST_H
+
+#include "naut/event.h"
+#include "naut/naut_plugin.h"
+#include "naut/rpc.h"
+
+typedef struct naut_plugin_manager naut_plugin_manager;
+
+naut_plugin_manager *naut_plugin_manager_create(
+    naut_rpc_registry *rpc, naut_event_bus *events);
+void naut_plugin_manager_destroy(naut_plugin_manager *manager);
+
+naut_err naut_plugin_load(naut_plugin_manager *manager, const char *path);
+
+size_t naut_plugin_count(const naut_plugin_manager *manager);
+const char *naut_plugin_name(const naut_plugin_manager *manager, size_t index);
+size_t naut_plugin_storage_count(const naut_plugin_manager *manager);
+const char *naut_plugin_storage_name(const naut_plugin_manager *manager,
+                                     size_t index);
+const naut_storage_backend_v1 *naut_plugin_storage_backend(
+    const naut_plugin_manager *manager, const char *name);
+
+#endif /* NAUT_PLUGIN_HOST_H */