Optional instant stage-fail when a survival gauge hits 0%

Context

LR2 aborts playback immediately ("閉店") when the HARD/HAZARD gauge empties; there is no way to keep playing (beatoraja's Gauge Auto Shift is the beatoraja-only escape hatch).

Since the wave-3 gauge alignment (commit 7bbf052), survival gauges (HARD / DEATH) collapse to 0% once they drop below 2% and never recover, and the run is reported as FAILED — but playback continues to the end of the chart by design (documented in packages/player/src/core/groove-gauge.ts).

Proposal

Add an opt-in "instant fail" behavior for survival gauges:

• when the gauge collapses to 0%, end the play session immediately (stop judging, drain audio, jump to the result path with FAILED),
• expose it as a PlayerOptions flag (and a TUI/web setting) rather than changing the default, so the current play-to-the-end behavior stays available for practice,
• stamp the fail time so result screens / skins can show where the run died (the beatoraja web skin adapter already latches TIMER_FAILED on the gauge crossing into 0).

Notes

Low priority; pure feature work on top of the already-correct FAILED accounting.

Start with packages/player/src/core/groove-gauge.ts to understand the existing 0% collapse and FAILED accounting, then trace PlayerOptions and the play-session result path. Check how TUI/web settings and the beatoraja web skin adapter expose gauge failure. Done means the opt-in setting stops playback at collapse, preserves the default behavior when disabled, and makes the fail time available to result screens or skins.