Integrate WebTorrent support from libtorrent

[QuixThe2nd]

Summary

This wires rtorrent up as the configuration, UI, RPC, and CI consumer of WebTorrent support implemented in rakshasa/libtorrent.

The WebRTC, WebSocket tracker, signaling, SDP/ICE, and DataChannel transport logic remains in libtorrent. rtorrent only detects support, exposes user-facing controls/status, and displays WebTorrent tracker/peer state.

Depends on rakshasa/libtorrent#796.

What Changed

• Add build-time WebTorrent integration:

  • --enable-webtorrent / default enabled
  • --disable-webtorrent
  • configure-time probe for the required libtorrent WebTorrent API
  • HAVE_LIBUTORRENT_WEBTORRENT only when the probe succeeds
  • rtorrent does not link libdatachannel directly; it consumes libtorrent through pkg-config

• Add RPC/config commands:

  • system.has_webtorrent
  • protocol.webtorrent
  • protocol.webtorrent.set
  • p.is_webtorrent
  • p.transport
  • t.type_str

• Mark safe RPC commands:

  • system.has_webtorrent
  • protocol.webtorrent
  • p.is_webtorrent
  • p.transport
  • t.type_str

• Add UI integration:

  • peer list TR column
    • WT for WebTorrent/WebRTC peers
    • -- for TCP peers
  • peer detail view shows Transport: WebRTC or TCP
  • tracker list shows WebSocket trackers as websocket
  • download info panel shows WebTorrent state:
    • enabled
    • disabled
    • not built

• Add documentation examples:

  • #protocol.webtorrent.set = yes
  • #protocol.webtorrent.set = no
  • note that WebTorrent requires a WebTorrent-enabled rakshasa/libtorrent
  • note that ws:// and wss:// trackers are handled by libtorrent

• Update CI workflows:

  • add matrix fields for default/WebTorrent libtorrent builds
  • add rtorrent WebTorrent build path
  • add disabled WebTorrent build coverage

• Preserve completed-session seeding behavior:

  • restored complete torrents load resume progress and publish a full bitfield before WebTorrent peers connect

Runtime Behavior

When built with WebTorrent-capable libtorrent:

• WebTorrent is enabled by default.
• protocol.webtorrent.set = no disables WebTorrent runtime behavior globally.
• protocol.webtorrent.set = yes re-enables it.
• ws:// and wss:// trackers are accepted and handled by libtorrent.

When built without WebTorrent-capable libtorrent:

• system.has_webtorrent returns 0
• protocol.webtorrent returns 0
• setting protocol.webtorrent.set = yes throws:
  • WebTorrent support is not available in this build.

Compatibility

Existing TCP peer behavior and existing tracker behavior remain unchanged for:

• HTTP trackers
• HTTPS trackers
• UDP trackers
• DHT trackers

Existing peer rate/choke/snub/ban/disconnect behavior is unchanged.

Testing

Tested locally on macOS against the matching libtorrent branch.

WebTorrent-enabled build:

• ./configure --enable-webtorrent
• make -j4
• make check
  • 2/2 rtorrent tests passed

Disabled build against libtorrent built with --disable-webtorrent:

• ./configure --disable-webtorrent
• make -j4
• make check
  • 2/2 rtorrent tests passed

End-to-end browser test:

• rtorrent seeded a fresh torrent with a wss://tracker.btorrent.xyz:443 tracker
• browser WebTorrent client loaded the .torrent
• browser connected to rtorrent as a WebTorrent/WebRTC peer
• browser received the piece and completed the file

Also verified:

• git diff --check clean
• rtorrent + ruTorrent run successfully against the WebTorrent-enabled build

[kingomarwashere]

LFG!!!