DVD: harden seek and menu-control transitions

[jzhvymetal]

Summary

• clamp invalid negative disc seeks
• complete or remove DVD direct-control jobs deterministically
• preserve authored stream choices and navigation state across transitions
• avoid lock starvation while DVD control work is pending

Validation

• Focused Java DVD control tests passed in the Vibe extraction workspace.

Review state

Draft: still requires the recorded physical-disc navigation and repeated-seek gate.

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This replaces OpenSageTV#11, which was opened against an intermediate fork instead of the canonical SageTV repository. The topic was replayed without patch changes onto the current canonical master.

Maintenance triage (2026-09-29)

Disposition: draft; demonstrated DVD symptom exists, but this patch is too broad for maintenance review.

Observed user-visible failure: Skip Back near the beginning of a remotely played DVD produced a negative target, followed by FLUSH and stalled playback. A focused clamp and physical Fire TV sequence corrected that case. The current branch also changes direct-control job lifetime, lock behavior, authored stream selection, and transition state, which are not all necessary to fix the negative-seek symptom.

Before requesting review, split the minimal negative-seek correction from the other behavior, provide the exact before/after trace and authored fixture steps, and run repeated menu/seek/audio/subpicture gates on stock clients and the Java/Ogle path. The remaining transition work stays out of the merge queue until independently reproduced.

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