fix(plugins): apply sub-delay to plugin current subtitle lookup

- subtitles.current() maps playback time onto the subtitle clock so retimed and repeated lines resolve to the right cue
- Add e2e coverage for repeated lines under sub-delay
- Document the timing behavior and update the changelog fragment

changes/plugin-system.md

@@ -7,4 +7,4 @@ area: plugins
 - Added an example `episode-tags` plugin that tags mined cards with the show and episode, such as `show::Frieren::S01E07`.
 - Added an example `auto-jimaku` plugin that opens the Jimaku search when a file starts without a Japanese subtitle track.
 - Added a versioned plugin API with standalone authoring types, cached playback snapshots, lifecycle cancellation and cleanup, and awaitable mpv commands. Async activation is bounded and actions wait only for their own plugin. Shutdown skips pending loads, runs each deactivation once, and blocks calls from disposed plugins.
-- Mining events preserve original and kept note ids with the media and subtitle captured when mining starts, so delayed enrichment and merges into older notes keep the source episode.
+- Mining events preserve original and kept note ids with the media and subtitle captured when mining starts, so delayed enrichment and merges into older notes keep the source episode. Plugin subtitle lookups account for subtitle delay and return timing on the subtitle file's timeline.