docs: move dead-not-skipped (FEAT-1) to TODO backlog, M4 = BUG-5 fix

REWORK_PLAN.md M4 = resolve initiative rotation corruption (BUG-5).
Mid-round add/revive corrupts rotation. RED locked.

TODO.md FEAT-1 = dead participants stay in turn order (user request,
Saturday game). Feature backlog, not milestone.

TODO.md

@@ -3,6 +3,20 @@
 Backlog of bugs + long-term items, from user. Milestones live in
 REWORK_PLAN.md.
 
+## Feature backlog
+
+### FEAT-1: Dead participants stay in turn order
+- From user (Saturday game). Moved out of REWORK_PLAN (not milestone).
+- Dead (HP=0) participants must NOT be skipped.
+- Current: dead → `isActive=false` → removed from turn order → skipped.
+- Desired: dead occupy initiative slot, turn still comes up. PCs get
+  death-save turn.
+- Affects: `shared/turn.js` `nextTurn` (filters `isActive`), `applyHpChange`
+  (sets isActive=false on death), `computeTurnOrderAfterRemoval`.
+- Characterization tests (`src/tests/Combat.characterization.test.js`) lock
+  CURRENT behavior — UPDATE to desired when implementing.
+- RED test locked (desired state): `shared/tests/turn.dead-skip.test.js`.
+
 ## Confirmed bugs (tests written, NOT fixed)
 
 ### BUG-1: addParticipant + pause/resume corrupts turn rotation