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

shared/tests/turn.logging.test.js

@@ -21,9 +21,9 @@ const {
   reorderParticipants, endEncounter,
 } = shared;
 
-function p(id, init) {
+function p(id, init, extra = {}) {
   return makeParticipant({ id, name: id, type: 'monster',
-    initiative: init, maxHp: 100, currentHp: 100 });
+    initiative: init, maxHp: 100, currentHp: 100, ...extra });
 }
 function enc(ps, extra = {}) {
   return { name:'t', participants:ps, isStarted:false, isPaused:false,
@@ -105,11 +105,11 @@ describe('Logging contract: mutating ops', () => {
   });
 
   test('deathSave logs', async () => {
-    const e = enc([p('a', 10), p('b', 7), p('c', 3)]);
+    const e = enc([p('a', 10), p('b', 7, { type: 'character' }), p('c', 3)]);
     const started = await startEncounter(e, ctx);  // 1 log
     const dying = await applyHpChange(started, 'b', 'damage', 100, ctx); // 2 logs
-    const r = await deathSave(dying, 'b', 'fail', 1, ctx);              // 3 logs
-    expect(r.status).toBe('pending');
+    const r = await deathSave(dying, 'b', 'fail', ctx);                 // 3 logs
+    expect(r.status).toBe('dying');
     expect(storage.logs()).toHaveLength(3);
     expectLastLogged(storage);
   });