fix: instant death triggering on retry in exercise mode

In exercise mode, after retry, judge.update was called with
res.time = exercise_range.start while note pointers were reset to 0,
causing all notes before the range start to be marked as Miss and
immediately triggering instant death.

Fix by adding Judge::advance_to which pre-marks notes before the given
time as Judged and advances the pointers, called after reset in exercise
mode. Also guard the instant death check to State::Playing only.

Closes #755

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

Author: Mivik

prpr/src/judge.rs

@@ -328,6 +328,22 @@ impl Judge {
         self.judgements.borrow_mut().clear();
     }
 
+    /// Advance note pointers past notes before time `t`, marking them as judged.
+    /// Used in exercise mode to skip notes before the exercise range start.
+    pub fn advance_to(&mut self, chart: &mut Chart, t: f64) {
+        for (line, (idx, st)) in chart.lines.iter_mut().zip(self.notes.iter_mut()) {
+            while *st < idx.len() {
+                let note = &mut line.notes[idx[*st] as usize];
+                if note.time as f64 >= t {
+                    break;
+                }
+                note.judge = JudgeStatus::Judged;
+                *st += 1;
+            }
+        }
+        self.last_time = t;
+    }
+
     pub fn commit(&mut self, t: f64, what: Judgement, line_id: u32, note_id: u32, diff: f64) {
         self.judgements.borrow_mut().push((t, line_id, note_id, Ok(what)));
         self.inner.commit(what, diff);

prpr/src/scene/game.rs

@@ -625,6 +625,9 @@ impl GameScene {
                     }
                     Some(0) => {
                         reset!(self, res, tm);
+                        if self.mode == GameMode::Exercise {
+                            self.judge.advance_to(&mut self.chart, self.exercise_range.start);
+                        }
                         #[cfg(target_env = "ohos")]
                         miniquad::native::set_interceptor_state(true);
                     }
@@ -1066,6 +1069,7 @@ impl Scene for GameScene {
             WHITE
         };
         if !self.dead
+            && matches!(self.state, State::Playing)
             && (self.res.config.mods.contains(Mods::INSTANT_DEATH_AP) && counts[1] + counts[2] + counts[3] > 0
                 || self.res.config.mods.contains(Mods::INSTANT_DEATH_FC) && counts[2] + counts[3] > 0)
         {