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/script.h

@@ -0,0 +1,36 @@
+/* script.h - sandboxed Lua event hooks on a dedicated bounded worker. */
+#ifndef NAUT_SCRIPT_H
+#define NAUT_SCRIPT_H
+
+#include "naut/event.h"
+
+typedef struct naut_script naut_script;
+
+typedef naut_err (*naut_script_move_file_cb)(void *context,
+                                             uint64_t torrent_id,
+                                             uint32_t file_index,
+                                             const char *destination);
+
+typedef struct {
+    uint64_t queued;
+    uint64_t handled;
+    uint64_t dropped;
+    uint64_t errors;
+    uint64_t move_requests;
+} naut_script_stats;
+
+/* script_path is loaded before the worker starts. queue_capacity bounds copied
+ * events and must be non-zero. The VM owns no filesystem or process APIs. */
+naut_script *naut_script_create(naut_event_bus *events,
+                                const char *script_path,
+                                size_t queue_capacity,
+                                naut_script_move_file_cb move_file,
+                                void *move_context,
+                                naut_err *error);
+void naut_script_destroy(naut_script *script);
+
+void naut_script_get_stats(const naut_script *script,
+                           naut_script_stats *stats);
+const char *naut_script_last_error(naut_script *script);
+
+#endif /* NAUT_SCRIPT_H */