webui: replace nautctl web server with a loadable plugin

Drop the web UI that was compiled into nautctl and serve the
torrent-ui front end (../torrent-ui/public) from a native plugin
(plugins/webui) loaded via `nautd --plugin`. The plugin talks to the
engine only through the host call_rpc ABI and adapts the daemon's RPC
surface to the qBittorrent-style contract the UI expects (snapshot/SSE,
torrent detail tabs, add/delete, cookie auth).

Also folds in the daemon refactor that owns per-torrent worker threads
and the swarm engine (naut_swarm) used by the plugin's data source.

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

examples/README.md

@@ -18,13 +18,10 @@ Movies (no detectable episode) go to `<SORTED_ROOT>/<Title>/<Title> (year).<ext>
 ### Use it
 
 ```sh
-# 1. edit SORTED_ROOT (and options) at the top of the script
-# 2. start the daemon with the script
-nautd --socket /tmp/nautd.sock --script examples/anime_sort.lua
-
-# 3. register each torrent's storage so the move can resolve + relocate its files
-nautctl --socket /tmp/nautd.sock add_torrent \
-  '{"torrent_id":1,"torrent":"show.torrent","root":"/downloads/1"}'
+# Start the engine, load the script, and add a download.
+nautd --socket /tmp/nautd.sock
+nautctl --socket /tmp/nautd.sock script examples/anime_sort.lua
+nautctl --socket /tmp/nautd.sock add show.torrent /downloads/1
 ```
 
 As each file completes you'll see, e.g.:

examples/anime_sort.lua

@@ -10,9 +10,9 @@
 -- without waiting for the rest of the torrent.
 --
 -- Install:
---   nautd --socket /tmp/nautd.sock --script examples/anime_sort.lua
---   nautctl --socket /tmp/nautd.sock add_torrent \
---     '{"torrent_id":1,"torrent":"show.torrent","root":"/downloads/1"}'
+--   nautd --socket /tmp/nautd.sock
+--   nautctl --socket /tmp/nautd.sock script examples/anime_sort.lua
+--   nautctl --socket /tmp/nautd.sock add show.torrent /downloads/1
 --
 -- The parser below is a VERBATIM COPY of examples/anitomy.lua (the sandbox has
 -- no `require`, so it must be inlined). Keep the two in sync; examples/
@@ -22,7 +22,7 @@
 -- CONFIG — edit these
 ----------------------------------------------------------------------
 
-local SORTED_ROOT       = "/sorted"   -- destination library root
+local SORTED_ROOT       = "/workspaces/source/ai-garbo/Naut-Torrent/sorted"   -- destination library root
 local ONLY_VIDEO        = true        -- skip non-video files (subs, nfo, samples)
 local KEEP_ORIGINAL_NAME = false      -- true: keep the original filename;
                                       -- false: rename to "Title - SNNENN.ext"

examples/test_anime_sort.lua

@@ -15,6 +15,13 @@ dofile(dir .. "anime_sort.lua")   -- defines on_file_complete + _G.anime_sort
 
 _G.print = realprint
 
+local configured_root = _G.anime_sort.destination({
+    title = "__ROOT_PROBE__",
+    file_name = "__ROOT_PROBE__.mkv",
+    extension = "mkv",
+}):match("^(.*)/__ROOT_PROBE__/__ROOT_PROBE__%.mkv$")
+assert(configured_root, "could not derive SORTED_ROOT from anime_sort.lua")
+
 local fails = 0
 local function fire(path)
     captured = nil
@@ -35,21 +42,21 @@ end
 
 -- episodes
 expect("/downloads/1/[HorribleSubs] Boku no Hero Academia - 12 [1080p].mkv",
-       "/sorted/Boku no Hero Academia/Season 01/Boku no Hero Academia - S01E12.mkv")
+       configured_root .. "/Boku no Hero Academia/Season 01/Boku no Hero Academia - S01E12.mkv")
 expect("/downloads/2/[Group] Attack on Titan S04E28 [BD 1080p HEVC].mkv",
-       "/sorted/Attack on Titan/Season 04/Attack on Titan - S04E28.mkv")
+       configured_root .. "/Attack on Titan/Season 04/Attack on Titan - S04E28.mkv")
 expect("/dl/[Commie] Steins;Gate 0 - 12 [BD 1080p].mkv",
-       "/sorted/Steins;Gate 0/Season 01/Steins;Gate 0 - S01E12.mkv")
+       configured_root .. "/Steins;Gate 0/Season 01/Steins;Gate 0 - S01E12.mkv")
 expect("Demon.Slayer.Kimetsu.no.Yaiba.S03E11.1080p.mkv",
-       "/sorted/Demon Slayer Kimetsu no Yaiba/Season 03/Demon Slayer Kimetsu no Yaiba - S03E11.mkv")
+       configured_root .. "/Demon Slayer Kimetsu no Yaiba/Season 03/Demon Slayer Kimetsu no Yaiba - S03E11.mkv")
 expect("/x/[Erai-raws] Jujutsu Kaisen 2nd Season - 17 [1080p].mkv",
-       "/sorted/Jujutsu Kaisen/Season 02/Jujutsu Kaisen - S02E17.mkv")
+       configured_root .. "/Jujutsu Kaisen/Season 02/Jujutsu Kaisen - S02E17.mkv")
 
 -- movies (no episode)
 expect("/m/[Group] A Silent Voice [BD 1080p FLAC].mkv",
-       "/sorted/A Silent Voice/A Silent Voice.mkv")
+       configured_root .. "/A Silent Voice/A Silent Voice.mkv")
 expect("/m/Spirited.Away.2001.1080p.BluRay.x264.mkv",
-       "/sorted/Spirited Away/Spirited Away (2001).mkv")
+       configured_root .. "/Spirited Away/Spirited Away (2001).mkv")
 
 -- non-video file must be skipped (no move queued)
 do