fix: prevent music canplay callback from interrupting ABS playback start

When absPlayItem() paused S.audio, the stale canplay listener from the
last playCurrent() call still had a matching _playGen value and would
call S.audio.play() — triggering absInterrupt() which immediately paused
the ABS audio. Fix: export cancelMusicAutoplay() that bumps _playGen
before pausing, invalidating any pending canplay/guard callbacks.

Also shrink OK button and widen time input in sleep timer.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

styles.css

@@ -956,7 +956,7 @@ nav{flex:1;overflow-y:auto;padding:4px 10px}
 .abs-sleep-custom-row input:focus{border-color:var(--accent)}
 .abs-sleep-custom-row input[type=number]::-webkit-inner-spin-button,.abs-sleep-custom-row input[type=number]::-webkit-outer-spin-button{-webkit-appearance:none;margin:0}
 .abs-sleep-custom-row input[type=number]{-moz-appearance:textfield}
-.abs-sleep-custom-ok{flex-shrink:0;padding:4px 10px;background:var(--accent);border:none;border-radius:6px;color:#fff;font-family:var(--font);font-size:12px;font-weight:600;cursor:pointer}
+.abs-sleep-custom-ok{flex-shrink:0;padding:3px 7px;background:var(--accent);border:none;border-radius:5px;color:#fff;font-family:var(--font);font-size:11px;font-weight:600;cursor:pointer}
 .abs-chapter-list{flex-shrink:0;overflow-y:auto;max-height:0;transition:max-height .3s ease;border-top:1px solid transparent}
 .abs-chapter-list.open{max-height:220px;border-color:var(--border)}
 .abs-ch-item{display:flex;align-items:center;gap:10px;padding:8px 20px;cursor:pointer;transition:background .15s}