Handle mpv reload buffering as same media

- Keep overlay alive across same-media mpv reloads
- Avoid rearming startup gate and repeating AniSkip lookups
- Add regression coverage for reload/end-file/file-loaded sequence

backlog/tasks/task-313 - Fix-mpv-buffering-reload-overlay-lifecycle.md

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+---
+id: TASK-313
+title: Fix mpv buffering reload overlay lifecycle
+status: To Do
+assignee: []
+created_date: '2026-05-02 22:12'
+labels:
+  - bug
+  - mpv
+  - overlay
+dependencies: []
+priority: high
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+macOS local playback can emit an mpv reload/end-file/file-loaded sequence during buffering. SubMiner should treat same-media reload churn as a continuation, not a fresh playback session, so the visible overlay remains available and startup-only tokenization/AniSkip work is not repeated unnecessarily.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [ ] #1 Same-media mpv reload buffering does not hide the visible overlay.
+- [ ] #2 Same-media mpv reload buffering does not re-arm the pause-until-ready startup gate or wait for a second tokenization-ready signal.
+- [ ] #3 Same-media mpv reload buffering does not repeat AniSkip lookup work for the already-loaded media.
+- [ ] #4 Normal new-file playback still clears per-media state, applies managed subtitle defaults, auto-starts/updates the overlay, and runs needed startup checks.
+- [ ] #5 Regression coverage exercises the buffering reload/end-file/file-loaded sequence in the mpv plugin lifecycle.
+<!-- AC:END -->