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/Participant.characterization.test.js

@@ -29,8 +29,9 @@ describe('Participant -> Firebase', () => {
     const p = call.data.participants[0];
     expect(p).toMatchObject({
       name: 'Goblin', type: 'monster', maxHp: 7, currentHp: 7,
-      isNpc: false, isActive: true, deathSaves: 0, isDying: false, conditions: [],
+      isActive: true, status: 'conscious', deathSaveSuccesses: 0, deathSaveFailures: 0, conditions: [],
     });
+    expect(p).not.toHaveProperty('isNpc');
     expect(p).toHaveProperty('id');
     expect(p).toHaveProperty('initiative');
   });
@@ -43,7 +44,7 @@ describe('Participant -> Firebase', () => {
     expect(p.initiative).toBeLessThanOrEqual(23);
   });
 
-  test('addMonster as NPC: isNpc true', async () => {
+  test('addMonster as NPC: type npc', async () => {
     await setupReady();
     const form = within(getParticipantForm());
     fireEvent.change(form.getByPlaceholderText('e.g., Dire Wolf'), { target: { value: 'Guard' } });
@@ -53,7 +54,8 @@ describe('Participant -> Firebase', () => {
       const p = lastEncCall()?.data?.participants?.[0];
       return p && p.name === 'Guard';
     });
-    expect(lastEncCall().data.participants[0].isNpc).toBe(true);
+    expect(lastEncCall().data.participants[0].type).toBe('npc');
+    expect(lastEncCall().data.participants[0]).not.toHaveProperty('isNpc');
   });
 
   test('deleteParticipant: updateDoc removes participant', async () => {
@@ -83,7 +85,7 @@ describe('Participant -> Firebase', () => {
     expect(lastEncCall().data.participants[0].currentHp).toBe(7);
   });
 
-  test('damage to 0 deactivates participant', async () => {
+  test('damage to 0 marks non-NPC monster dead and inactive', async () => {
     await setupReady();
     await addMonsterViaUI('Doom', 5, 0);
     await startCombatViaUI();
@@ -92,10 +94,11 @@ describe('Participant -> Firebase', () => {
     await waitFor(() => lastEncCall()?.data?.participants?.[0]?.currentHp === 0);
     const p = lastEncCall().data.participants[0];
     expect(p.currentHp).toBe(0);
+    expect(p.status).toBe('dead');
     expect(p.isActive).toBe(false);
   });
 
-  test('heal revives from 0 (reactivates, resets death saves)', async () => {
+  test('normal heal does not revive dead non-NPC monster', async () => {
     await setupReady();
     await addMonsterViaUI('Revive', 5, 0);
     await startCombatViaUI();
@@ -104,11 +107,10 @@ describe('Participant -> Firebase', () => {
     await waitFor(() => lastEncCall()?.data?.participants?.[0]?.currentHp === 0);
     fireEvent.change(screen.getByPlaceholderText('HP'), { target: { value: '3' } });
     fireEvent.click(screen.getByTitle(/Heal/i));
-    await waitFor(() => lastEncCall()?.data?.participants?.[0]?.currentHp === 3);
+    await waitFor(() => lastEncCall()?.data?.participants?.[0]?.status === 'dead');
     const p = lastEncCall().data.participants[0];
-    expect(p.currentHp).toBe(3);
-    expect(p.isActive).toBe(true);
-    expect(p.deathSaves).toBe(0);
+    expect(p.currentHp).toBe(0);
+    expect(p.status).toBe('dead');
   });
 
   test('toggleCondition: updateDoc adds condition to array', async () => {