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/run_phase7.sh

@@ -0,0 +1,98 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+daemon=$1
+ctl=$2
+plugin=$3
+script=$4
+tmp=$(mktemp -d)
+socket="$tmp/nautd.sock"
+daemon_log="$tmp/nautd.log"
+events_log="$tmp/events.log"
+
+cleanup() {
+    result=$?
+    if [[ -n "${daemon_pid:-}" ]]; then
+        kill "$daemon_pid" 2>/dev/null || true
+        wait "$daemon_pid" 2>/dev/null || true
+    fi
+    if [[ -n "${events_pid:-}" ]]; then
+        kill "$events_pid" 2>/dev/null || true
+        wait "$events_pid" 2>/dev/null || true
+    fi
+    if [[ "$result" -ne 0 ]]; then
+        cat "$daemon_log" >&2 2>/dev/null || true
+        cat "$events_log" >&2 2>/dev/null || true
+    fi
+    rm -rf "$tmp"
+    return "$result"
+}
+trap cleanup EXIT
+
+"$daemon" --socket "$socket" --plugin "$plugin" --script "$script" \
+    >"$daemon_log" 2>&1 &
+daemon_pid=$!
+
+for _ in $(seq 1 100); do
+    [[ -S "$socket" ]] && break
+    sleep 0.02
+done
+[[ -S "$socket" ]]
+
+"$ctl" --socket "$socket" ping | grep -q '"service": "nautd"'
+"$ctl" --socket "$socket" plugins | grep -q '"memory"'
+
+timeout 5 "$ctl" --socket "$socket" events >"$events_log" &
+events_pid=$!
+sleep 0.1
+"$ctl" --socket "$socket" emit \
+    '{"type":"torrent_finished","torrent_id":7}' >/dev/null
+
+status=
+for _ in $(seq 1 100); do
+    status=$("$ctl" --socket "$socket" status)
+    if grep -q '"move_commands": 1' <<<"$status" &&
+       grep -q '"handled": 1' <<<"$status"; then
+        break
+    fi
+    sleep 0.02
+done
+grep -q '"move_commands": 1' <<<"$status"
+grep -q '"handled": 1' <<<"$status"
+grep -q '"errors": 0' <<<"$status"
+
+plugin_status=$("$ctl" --socket "$socket" example.events)
+grep -q '"finished": 1' <<<"$plugin_status"
+
+for _ in $(seq 1 100); do
+    grep -q '"event": "torrent_finished"' "$events_log" && break
+    sleep 0.02
+done
+grep -q '"event": "torrent_finished"' "$events_log"
+
+# --- end-to-end move-as-you-finish: register a real torrent's storage, fire a
+# file_complete event, and confirm the script-driven move actually relocates the
+# file on disk (script thread -> bounded queue -> owner thread -> storage). ----
+fixtures=$(dirname "$script")
+root="$tmp/torrent-data"
+"$ctl" --socket "$socket" add_torrent \
+    "{\"torrent_id\":42,\"torrent\":\"$fixtures/single_v1.torrent\",\"root\":\"$root\"}" \
+    | grep -q '"ok": true'
+
+src=$(find "$root" -type f | head -n1)
+[[ -n "$src" ]]
+
+"$ctl" --socket "$socket" emit \
+    "{\"type\":\"file_complete\",\"torrent_id\":42,\"index\":0,\"path\":\"$src\"}" \
+    >/dev/null
+
+for _ in $(seq 1 100); do
+    [[ -f "$src.moved" ]] && break
+    sleep 0.02
+done
+[[ -f "$src.moved" ]]
+[[ ! -f "$src" ]]
+
+"$ctl" --socket "$socket" shutdown >/dev/null
+wait "$daemon_pid"
+daemon_pid=