tests: M4 dead-participant skip RED (4 tests, turn.dead-skip.test.js)

Desired behavior locked:
- dead PC not removed from turnOrderIds
- dead PC turn still comes up (nextTurn visits them)
- dead PC on their turn can deathSave
- dead PC not auto-set isActive=false by applyHpChange

All 4 RED on current code. Root cause: nextTurn filters isActive,
applyHpChange sets isActive=false on death, computeTurnOrderAfterRemoval
drops dead from turnOrderIds.

TODO BUG-3/M4 updated with test refs.

TODO.md

@@ -2,7 +2,7 @@
 
 ## M4 — Initiative skip bug + dead-participant handling
 
-### Dead participants must NOT be skipped in turn order
+### Dead participants must NOT be skipped in turn order (BUG-3 / M4)
 - Current: dead (HP=0) → `isActive=false` → removed from turn order → skipped
 - WRONG. Dead participants still occupy initiative slot.
   - PCs (unconscious): death saves still resolve on their turn
@@ -14,7 +14,12 @@
   (sets isActive=false on death), `computeTurnOrderAfterRemoval`.
 - Characterization tests (`src/tests/Combat.characterization.test.js`) lock CURRENT
   (buggy) behavior — those tests must be UPDATED to desired behavior, not
-  preserved. Red desired-test first, then fix.
+  preserved.
+- RED test locked: `shared/tests/turn.dead-skip.test.js` (4 tests).
+  - dead PC not removed from turnOrderIds
+  - dead PC turn still comes up (nextTurn visits them)
+  - dead PC on their turn can deathSave
+  - dead PC not auto-set isActive=false by applyHpChange
 
 ### JUMP_TURN_TO(participantId) manual turn override
 - DM clicks participant → cursor jumps → that participant's turn now.

shared/tests/turn.dead-skip.test.js

@@ -0,0 +1,73 @@
+// M4 desired behavior: dead PC stays in turn order, turn still comes up,
+// deathSave fires. Current code filters isActive (set false on death) so
+// dead participants are SKIPPED. Test asserts desired state = RED on current.
+
+const shared = require('@ttrpg/shared');
+const { makeParticipant, startEncounter, nextTurn, applyHpChange, deathSave } = shared;
+
+function p(id, init, extra = {}) {
+  return makeParticipant({
+    id, name: id, type: 'monster',
+    initiative: init, maxHp: 100, currentHp: 100,
+    ...extra,
+  });
+}
+function pc(id, init, extra = {}) {
+  return makeParticipant({
+    id, name: id, type: 'character',
+    initiative: init, maxHp: 100, currentHp: 100,
+    ...extra,
+  });
+}
+function enc(ps) {
+  return { name:'t', participants:ps, isStarted:false, isPaused:false,
+    round:0, currentTurnParticipantId:null, turnOrderIds:[] };
+}
+
+describe('M4: dead participants stay in turn order', () => {
+  test('dead PC not removed from turnOrderIds', () => {
+    const ps = [pc('a', 20), pc('b', 15), pc('c', 10)];
+    let e = enc(ps);
+    e = { ...e, ...startEncounter(e).patch };
+    const orderBefore = e.turnOrderIds.slice();
+    // kill b
+    e = { ...e, ...applyHpChange(e, 'b', 'damage', 100).patch };
+    expect(e.turnOrderIds).toEqual(orderBefore);
+  });
+
+  test('dead PC turn still comes up (nextTurn visits them)', () => {
+    const ps = [pc('a', 20), pc('b', 15), pc('c', 10)];
+    let e = enc(ps);
+    e = { ...e, ...startEncounter(e).patch };
+    // kill b
+    e = { ...e, ...applyHpChange(e, 'b', 'damage', 100).patch };
+    // advance: a→b→c. b's turn should come up.
+    e = { ...e, ...nextTurn(e).patch };
+    expect(e.currentTurnParticipantId).toBe('b');
+  });
+
+  test('dead PC on their turn can deathSave', () => {
+    const ps = [pc('a', 20), pc('b', 15)];
+    let e = enc(ps);
+    e = { ...e, ...startEncounter(e).patch };
+    // kill b (current = a)
+    e = { ...e, ...applyHpChange(e, 'b', 'damage', 100).patch };
+    // advance to b's turn
+    e = { ...e, ...nextTurn(e).patch };
+    expect(e.currentTurnParticipantId).toBe('b');
+    // b is dead, on their turn: deathSave should not throw
+    const r = deathSave(e, 'b', 1);
+    expect(r.patch).toBeTruthy();
+    const b = r.patch.participants.find(x => x.id === 'b');
+    expect(b.deathSaves).toBe(1);
+  });
+
+  test('dead PC not auto-set isActive=false by applyHpChange', () => {
+    const ps = [pc('a', 20), pc('b', 15)];
+    let e = enc(ps);
+    e = { ...e, ...startEncounter(e).patch };
+    e = { ...e, ...applyHpChange(e, 'b', 'damage', 100).patch };
+    const b = e.participants.find(x => x.id === 'b');
+    expect(b.isActive).toBe(true);
+  });
+});