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.

src/tests/Combat.scenario.test.js

@@ -160,10 +160,10 @@ function removeParticipantByName(name) {
   if (!p) throw new Error(`no remove target: ${name}`);
   applyEnc(removeParticipant(enc, p.id).patch);
 }
-function deathSaveAction(name, saveNum) {
+function deathSaveAction(name, type, saveNum) {
   const p = any(name);
   if (!p) throw new Error(`no deathsave target: ${name}`);
-  applyEnc(combatDeathSave(enc, p.id, saveNum).patch);
+  applyEnc(combatDeathSave(enc, p.id, type, saveNum).patch);
 }
 function dragTie(draggedName, targetName) {
   const d = any(draggedName), t = any(targetName);
@@ -254,16 +254,16 @@ test('full 100-round combat scenario (shared, no React)', async () => {
     // death scenarios: drop a PC to 0, death saves, revive
     if (r === 25 && turnInRound === 0) {
       await recordAsync(`r${r} drop Rogue`, () => applyDamage('Rogue', 99));
-      record(`r${r} deathSave1 Rogue`, () => deathSaveAction('Rogue', 1));
+      record(`r${r} deathSave1 Rogue`, () => deathSaveAction('Rogue', 'fail', 1));
       record(`r${r} revive Rogue`, () => applyHeal('Rogue', 22));
     }
     // round 50: full 3-success death-save path (isDying) on Cleric, then remove
     if (r === 50 && turnInRound === 0) {
       await recordAsync(`r${r} drop Cleric`, () => applyDamage('Cleric', 99));
       await recordAsync(`r${r} deathSave Cleric x3 (isDying)`, async () => {
-        deathSaveAction('Cleric', 1);
-        deathSaveAction('Cleric', 2);
-        deathSaveAction('Cleric', 3); // → isDying true
+        deathSaveAction('Cleric', 'fail', 1);
+        deathSaveAction('Cleric', 'fail', 2);
+        deathSaveAction('Cleric', 'fail', 3); // → dead
       });
       const cl = any('Cleric');
       if (cl && cl.isDying) record(`r${r} remove dying Cleric`, () => removeParticipantByName('Cleric'));