Implement D&D 5e death-save state machine and cleanup combat ordering

- Add status-driven death-save model:
  - status: conscious | dying | stable | dead
  - deathSaveSuccesses/deathSaveFailures as display counters
  - remove old death-save fields as source of truth
- Add death-save actions:
  - success, fail, nat1, nat20
  - stabilize participant
  - revive dead participant to 0 HP, stable, unconscious
- Apply 5e HP transition rules:
  - characters and NPCs at 0 HP become dying
  - stable/dying participants gain unconscious condition
  - healing clears death saves and returns conscious
  - massive damage kills
  - non-NPC monsters at 0 HP become dead and inactive
- Split NPCs from monsters with type="npc":
  - NPCs use death saves like characters
  - NPCs remain DM-controlled/monster-colored in UI
  - new NPCs no longer persist isNpc flag
- Keep dead PCs/NPCs in encounter and initiative until DM removes or deactivates
- Allow DM active/inactive toggle for dead participants
- Hide inactive participants from player display
- Improve DM and player death-state UI:
  - show Dying/Dead/Unconscious states consistently
  - add revive button for dead participants
  - distinguish dead visual from inactive visual in DM view
- Fix initiative drag/reorder behavior:
  - downward drag now changes order instead of no-op
  - paused combat can reorder across current turn pointer
  - turnOrderIds stay synced to participants order
- Persist campaign collapse state in localStorage
- Update death-save docs and encounter builder docs
- Add/expand tests for:
  - death saves and HP transitions
  - dead/active/inactive behavior
  - NPC death-save behavior
  - player display visibility
  - drag reorder semantics
  - logging expectations

Tests:
- npm run test:all
- app: 94 passed
- shared: 158 passed, 5 skipped
- server: 32 passed

scripts/combat/replay.js

@@ -301,11 +301,11 @@ module.exports = async function replay(args) {
           (e) => updateParticipant(e, actor.id, { notes: `edited r${enc.round}` }, ctx))).enc;
       }
 
-      if (actor.currentHp <= 0 && !actor.isNpc) {
+      if (actor.status === 'dying' && !actor.isNpc) {
         if (VERBOSE) console.log(`    deathSave ${actor.name} +1 success`);
         enc = (await callStep('deathSave',
-          { participant: actor.name, type: 'success', n: 1 },
-          (e) => deathSave(e, actor.id, 'success', 1, ctx))).enc;
+          { participant: actor.name, outcome: 'success' },
+          (e) => deathSave(e, actor.id, 'success', ctx))).enc;
       }
 
       if (totalTurns % 9 === 0) {