refactor: App.js 3 sites to shared 1-list contract

delete/toggle/hp sites used OLD computeTurnOrderAfterRemoval/Addition
contract (return turnOrderIds). New 1-list contract: helpers return
advance-only + insertAt; list sync via syncTurnOrder at call site.

- delete: syncTurnOrder(updated) + advance-only removal
- toggle: stay-in-slot, flip isActive, sync, advance only if deact==current
- hp: FEAT-1 unchanged (death/revive no turn changes)

shared exports syncTurnOrder. Build green.

shared/turn.js

@@ -565,6 +565,7 @@ module.exports = {
   rollD20,
   formatInitMod,
   sortParticipantsByInitiative,
+  syncTurnOrder,
   computeTurnOrderAfterRemoval,
   computeTurnOrderAfterAddition,
   makeParticipant,