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>

tests/integration/http_tracker.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+"""Minimal compact-peer HTTP tracker for the Phase 4 integration test."""
+from http.server import BaseHTTPRequestHandler, HTTPServer
+import socket
+import struct
+import sys
+
+peer_port = int(sys.argv[1])
+body = (
+    b"d8:intervali1800e5:peers6:"
+    + socket.inet_aton("127.0.0.1")
+    + struct.pack("!H", peer_port)
+    + b"e"
+)
+
+
+class Tracker(BaseHTTPRequestHandler):
+    def do_GET(self):
+        self.send_response(200)
+        self.send_header("Content-Type", "text/plain")
+        self.send_header("Content-Length", str(len(body)))
+        self.end_headers()
+        self.wfile.write(body)
+
+    def log_message(self, fmt, *args):
+        print("REQUEST " + (fmt % args), flush=True)
+
+
+server = HTTPServer(("127.0.0.1", 0), Tracker)
+print("PORT %d" % server.server_port, flush=True)
+server.serve_forever()