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

src/tests/Combat.scenario.test.js

@@ -75,8 +75,8 @@ function addCharacterViaUI(name, maxHp, initMod) {
   roster.push({ id: `char-${name}`, name, defaultMaxHp: maxHp, defaultInitMod: initMod });
 }
 
-async function addMonsterParticipant(name, maxHp, initMod, isNpc = false) {
-  const { participant } = buildMonsterParticipant({ name, maxHp, initMod, isNpc });
+async function addMonsterParticipant(name, maxHp, initMod, asNpc = false) {
+  const { participant } = buildMonsterParticipant({ name, maxHp, initMod, asNpc });
   enc = await addParticipant(enc, participant, ctx);
 }
 async function addCharacterParticipant(charName) {
@@ -140,10 +140,10 @@ async function removeParticipantByName(name) {
   if (!p) throw new Error(`no remove target: ${name}`);
   enc = await removeParticipant(enc, p.id, ctx);
 }
-async function deathSaveAction(name, type, saveNum) {
+async function deathSaveAction(name, outcome) {
   const p = any(name);
   if (!p) throw new Error(`no deathsave target: ${name}`);
-  const r = await combatDeathSave(enc, p.id, type, saveNum, ctx);
+  const r = await combatDeathSave(enc, p.id, outcome, ctx);
   enc = r.enc;
 }
 async function dragTie(draggedName, targetName) {
@@ -221,19 +221,22 @@ test('full 100-round combat scenario (shared, no React)', async () => {
     }
 
     if (r === 25 && turnInRound === 0) {
-      await record(`r${r} drop Rogue`, () => applyDamage('Rogue', 99));
-      await record(`r${r} deathSave1 Rogue`, () => deathSaveAction('Rogue', 'fail', 1));
+      await record(`r${r} drop Rogue`, () => applyDamage('Rogue', any('Rogue').currentHp));
+      await record(`r${r} deathSave1 Rogue`, () => deathSaveAction('Rogue', 'fail'));
       await record(`r${r} revive Rogue`, () => applyHeal('Rogue', 22));
     }
     if (r === 50 && turnInRound === 0) {
-      await record(`r${r} drop Cleric`, () => applyDamage('Cleric', 99));
-      await record(`r${r} deathSave Cleric x3 (isDying)`, async () => {
-        await deathSaveAction('Cleric', 'fail', 1);
-        await deathSaveAction('Cleric', 'fail', 2);
-        await deathSaveAction('Cleric', 'fail', 3);
+      await record(`r${r} drop Cleric`, () => applyDamage('Cleric', any('Cleric').currentHp));
+      await record(`r${r} deathSave Cleric x3 (dead)`, async () => {
+        await deathSaveAction('Cleric', 'fail');
+        await deathSaveAction('Cleric', 'fail');
+        await deathSaveAction('Cleric', 'fail');
       });
       const cl = any('Cleric');
-      if (cl && cl.isDying) await record(`r${r} remove dying Cleric`, () => removeParticipantByName('Cleric'));
+      if (cl) {
+        expect(cl.status).toBe('dead');
+        expect(enc.participants.map(p => p.name)).toContain('Cleric');
+      }
     }
 
     if (r % 30 === 0 && turnInRound === 1) {