feat(turn): D&D 5e death saves — success/fail tracking

Old model broken: single deathSaves counter, 3=revive. No fails tracked,
successes conflated with fails. DM couldn't model real death save outcomes.

New model (D&D 5e):
- deathSave(enc, id, type, n) — type='success'|'fail', n=1|2|3
- Participant fields: deathSaves (successes), deathFails, isStable, isDying
- 3 successes = stable (0hp unconscious, safe until healed)
- 3 failures = dead (isDying, caller animates removal)
- Toggling same pip = undo that pip
- Returns { patch, log, status } — status: 'stable'|'dead'|'pending'
  isDying back-compat flag kept for App.js removal animation

App.js:
- UI split into green ✓ saves row + red ✕ fails row
- Status badges: Stabilized (emerald) / Dying (red pulse)
- handleDeathSaveChange(participantId, type, saveNumber) — new sig
- makeParticipant init: deathFails + isStable defaults

Data loss: old single-counter participants lose saves (feature didn't work,
no real state to preserve). User confirmed acceptable.

Tests:
- turn.deathsave.test.js: RED-then-GREEN, 3-success stable, 3-fail dead,
  independent tracking, new signature
- Updated 6 callers across characterization/combat/dead-skip/logging/scenario
- Logs UI tests: new title selectors (Success N / Fail N)

243 tests green.

shared/turn.js

@@ -129,7 +129,9 @@ function makeParticipant(opts) {
     isNpc: opts.isNpc || false,
     conditions: opts.conditions || [],
     isActive: opts.isActive !== undefined ? opts.isActive : true,
-    deathSaves: opts.deathSaves || 0,
+    deathSaves: opts.deathSaves || 0,  // successes (0-3)
+    deathFails: opts.deathFails || 0,  // failures (0-3)
+    isStable: opts.isStable || false,
     isDying: opts.isDying || false,
   };
 }
@@ -492,41 +494,63 @@ function applyHpChange(encounter, participantId, changeType, amount) {
   };
 }
 
-// DEATH_SAVE — verbatim from ParticipantManager.handleDeathSaveChange
-// saveNumber: 1 | 2 | 3. Returns isDying flag if 3rd save hit (client triggers removal animation).
-function deathSave(encounter, participantId, saveNumber) {
+// DEATH_SAVE — D&D 5e model. Separate success/fail tracking.
+//   type: 'success' | 'fail'
+//   n: 1 | 2 | 3 (which pip clicked)
+// 3 successes = stable (0hp unconscious, safe). 3 fails = dead (isDying,
+//   caller animates removal). Toggling same pip = undo that pip.
+// Returns { patch, log, status } where status: 'stable'|'dead'|'pending'.
+function deathSave(encounter, participantId, type, n) {
   const participant = (encounter.participants || []).find(p => p.id === participantId);
   if (!participant) throw new Error('Participant not found.');
-  const currentSaves = participant.deathSaves || 0;
-  const newSaves = currentSaves === saveNumber ? saveNumber - 1 : saveNumber;
+  if (type !== 'success' && type !== 'fail') {
+    throw new Error(`deathSave type must be 'success' or 'fail', got "${type}".`);
+  }
   const name = participant.name;
   const undo = { participants: encounter.participants || [] };
 
-  if (newSaves === 3) {
-    // Mark dying — caller waits for animation, then calls removeParticipant.
-    const updatedParticipants = (encounter.participants || []).map(p =>
-      p.id === participantId ? { ...p, deathSaves: newSaves, isDying: true } : p
-    );
-    return {
-      patch: { participants: updatedParticipants },
-      log: {
-        message: `${name} failed 3 death saves — dying`,
-        undo,
-      },
-      isDying: true,
-    };
+  // Toggle: clicking current-value pip decrements (undo that pip).
+  const current = type === 'success'
+    ? (participant.deathSaves || 0)
+    : (participant.deathFails || 0);
+  const next = current === n ? n - 1 : n;
+
+  const field = type === 'success' ? 'deathSaves' : 'deathFails';
+  const updates = { [field]: next };
+
+  // Clear terminal flags on any change (re-eval below).
+  let status = 'pending';
+  const newSuccesses = type === 'success' ? next : (participant.deathSaves || 0);
+  const newFails = type === 'fail' ? next : (participant.deathFails || 0);
+
+  if (newSuccesses >= 3) {
+    updates.isStable = true;
+    updates.isDying = false;
+    status = 'stable';
+  } else if (newFails >= 3) {
+    updates.isStable = false;
+    updates.isDying = true;
+    status = 'dead';
+  } else {
+    updates.isStable = false;
+    updates.isDying = false;
   }
 
   const updatedParticipants = (encounter.participants || []).map(p =>
-    p.id === participantId ? { ...p, deathSaves: newSaves } : p
+    p.id === participantId ? { ...p, ...updates } : p
   );
+
+  const message = status === 'stable'
+    ? `${name} stabilized (3 death saves)`
+    : status === 'dead'
+      ? `${name} failed 3 death saves — dead`
+      : `${name} death ${type}: ${next}/3`;
+
   return {
     patch: { participants: updatedParticipants },
-    log: {
-      message: `${name} death save: ${newSaves}/3`,
-      undo,
-    },
-    isDying: false,
+    log: { message, undo },
+    status,
+    isDying: status === 'dead', // back-compat for App.js handler
   };
 }