Restore anime episode progress from subtitle timing

- Fall back to latest retained subtitle/event segment end when `ended_media_ms` is missing
- Tighten stats command tests and add regression coverage for the fallback

backlog/tasks/task-211 - Recover-anime-episode-progress-from-subtitle-timing-when-checkpoints-are-missing.md

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+---
+id: TASK-211
+title: Recover anime episode progress from subtitle timing when checkpoints are missing
+status: Done
+assignee:
+  - '@Codex'
+created_date: '2026-03-20 10:15'
+updated_date: '2026-03-20 10:22'
+labels:
+  - stats
+  - bug
+milestone: m-1
+dependencies: []
+references:
+  - src/core/services/immersion-tracker/query.ts
+  - src/core/services/immersion-tracker/__tests__/query.test.ts
+---
+
+## Description
+
+Anime episode progress can still show `0%` for older sessions that have watch-time and subtitle timing but no persisted `ended_media_ms` checkpoint. Recover progress from the latest retained subtitle/event segment end so already-recorded sessions render a useful progress percentage.
+
+## Acceptance Criteria
+
+- [x] `getAnimeEpisodes` returns the latest known session position even when `ended_media_ms` is null but subtitle/event timing exists.
+- [x] Existing ended-session metrics and aggregation totals do not regress.
+- [x] Regression coverage locks the fallback behavior.
+
+## Implementation Notes
+
+Added a query-side fallback for anime episode progress: when the newest session for a video has no persisted `ended_media_ms`, `getAnimeEpisodes` now uses the latest retained subtitle-line or session-event `segment_end_ms` from that same session. This recovers useful progress for already-recorded sessions that have timing data but predate or missed checkpoint persistence.
+
+Verification: `bun test src/core/services/immersion-tracker/__tests__/query.test.ts` passed. `bun run typecheck` passed.