M4 — channel browse + context-menu drill-down

Sidecar ChannelVideos op via rustypipe channel_videos(). Returns the
channel metadata block (id, name, subscribers, banner) alongside the
items array — same VideoItem shape as search.

Addon refactor: _add_video_items is now the shared listing builder.
Both _search_directory and _channel_directory call it. Each video
result gets a 'Go to <channel>' context-menu entry that
Container.Update's to ?action=channel&id=<channel_id> — so from any
search result, the user can drill into that channel's recent uploads
without going back through search.

Smoke verified on the Pi via Files.GetDirectory: LTT channel
(UCXuqSBlHAE6Xw-yeJA0Tunw) returned 30 recent videos.

Addon version 0.0.7.

addon/plugin.video.torttube/addon.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 <addon id="plugin.video.torttube"
        name="torttube"
-       version="0.0.6"
+       version="0.0.7"
        provider-name="Sulkta">
   <requires>
     <import addon="xbmc.python" version="3.0.0"/>