chore(backlog): maintain task backlog and add changelog fragments

- Move completed tasks (85, 117, 118, 155) to backlog/completed/
- Delete superseded task files (166 verification, 172 drilldown)
- Add stats dashboard milestone m-1
- Add new tasks (190, 194)
- Update task metadata across remaining backlog items
- Add changelog fragments for stats, mpv args, and subtitle filtering

changes/2026-03-18-stats-cross-anime-words-table.md

@@ -0,0 +1,4 @@
+type: fixed
+area: stats
+
+- Restored the cross-anime word table behavior in stats vocabulary surfaces so shared vocabulary entries no longer disappear or merge incorrectly across related media.

changes/2026-03-18-stats-full-session-timelines.md

@@ -0,0 +1,4 @@
+type: fixed
+area: stats
+
+- Load full session timelines by default in stats session detail views so long sessions preserve complete telemetry history instead of being truncated by a fixed sample limit.

changes/2026-03-18-stats-mpv-args-passthrough.md

@@ -0,0 +1,4 @@
+type: added
+area: launcher
+
+- Added launcher passthrough for `-a/--args` so mpv receives raw extra launch flags (`--fs`, `--ytdl-format`, custom audio/video settings, etc.) from the `subminer` command.

changes/2026-03-18-subtitle-noise-filtering.md

@@ -0,0 +1,4 @@
+type: changed
+area: overlay
+
+- Excluded interjections and sound-effect tokens from subtitle annotation styling so they no longer inherit misleading lexical highlight treatment while still remaining visible and non-interactive in the subtitle line.