M3: add combat replay script + TODO for M4 skip/dead fixes

scripts/replay-combat.js: drives full combat via live backend REST, computes
turns through shared/turn.js. Player display (subscribed via WS) live-updates.
Usage: node scripts/replay-combat.js [rounds] [delayMs]

TODO.md: tracks M4 work.
  - Dead participants must NOT be skipped (still occupy initiative slot,
    death saves resolve on their turn). Saw in game Saturday.
  - JUMP_TURN_TO manual turn override.

TODO.md

@@ -0,0 +1,33 @@
+# TODO
+
+## M4 — Initiative skip bug + dead-participant handling
+
+### Dead participants must NOT be skipped in turn order
+- 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
+  - Monsters/NPCs: may still have reaction/reaction-like considerations
+- Saw this problem in game Saturday.
+- Fix: keep dead participants in turnOrderIds; their turn still comes up.
+  Damage/death-save UI already gated on HP=0 so row buttons stay usable.
+- Affects: `shared/turn.js` `nextTurn` (filters `isActive`), `applyHpChange`
+  (sets isActive=false on death), `computeTurnOrderAfterRemoval`.
+- Characterization 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.
+
+### JUMP_TURN_TO(participantId) manual turn override
+- DM clicks participant → cursor jumps → that participant's turn now.
+- Future NEXT_TURN continues from jumped position.
+- UI button: "Make This Turn"
+- Backend action: new endpoint or via generic doc patch.
+
+## Pipeline
+- [ ] Red test: dead participant still in turnOrderIds, turn still advances to them
+- [ ] Fix `shared/turn.js`: don't drop dead from turn order
+- [ ] Update characterization tests to desired (not preserved) behavior
+- [ ] JUMP_TURN_TO red test
+- [ ] JUMP_TURN_TO impl (shared + UI button)
+- [ ] M5 docker-compose
+- [ ] M6 undo rework (transactional events table)
+- [ ] M7 Playwright E2E