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/tests/turn.characterization.test.js

@@ -247,22 +247,22 @@ describe('applyHpChange', () => {
 });
 
 describe('deathSave', () => {
-  test('increments saves', () => {
-    const ps = [p('a', 10, { currentHp: 0, deathSaves: 0 })];
-    const { patch } = deathSave(enc(ps), 'a', 1);
-    expect(patch.participants[0].deathSaves).toBe(1);
+  test('increments fails', () => {
+    const ps = [p('a', 10, { currentHp: 0, deathFails: 0 })];
+    const { patch } = deathSave(enc(ps), 'a', 'fail', 1);
+    expect(patch.participants[0].deathFails).toBe(1);
   });
 
-  test('clicking same save decrements (toggle)', () => {
-    const ps = [p('a', 10, { currentHp: 0, deathSaves: 2 })];
-    const { patch } = deathSave(enc(ps), 'a', 2);
-    expect(patch.participants[0].deathSaves).toBe(1);
+  test('clicking same fail decrements (toggle)', () => {
+    const ps = [p('a', 10, { currentHp: 0, deathFails: 2 })];
+    const { patch } = deathSave(enc(ps), 'a', 'fail', 2);
+    expect(patch.participants[0].deathFails).toBe(1);
   });
 
-  test('third save sets isDying', () => {
-    const ps = [p('a', 10, { currentHp: 0, deathSaves: 2 })];
-    const result = deathSave(enc(ps), 'a', 3);
-    expect(result.patch.participants[0].deathSaves).toBe(3);
+  test('third fail sets isDying', () => {
+    const ps = [p('a', 10, { currentHp: 0, deathFails: 2 })];
+    const result = deathSave(enc(ps), 'a', 'fail', 3);
+    expect(result.patch.participants[0].deathFails).toBe(3);
     expect(result.patch.participants[0].isDying).toBe(true);
     expect(result.isDying).toBe(true);
   });