fix(BUG-4): updateDoc patch on activeDisplay (not setDoc replace)

All 5 storage.setDoc(activeDisplay, {...}, {merge:true}) →
storage.updateDoc(activeDisplay, {...}).

setDoc merge:true worked in prod (firebase honors merge) but ws adapter
+ mock ignore opts arg entirely → clobbers doc. updateDoc uses PATCH
across all adapters (firebase real updateDoc, ws PATCH endpoint, mock
merge). Consistent, no clobber.

Sites fixed:
- hidePlayerHp toggle
- startEncounter (set active ids)
- endEncounter (null active ids)
- deactivate active display
- activate new display

TDD: HideHpToggle.test RED first (assert updateDoc patch, impl still
setDoc → 0 calls found). GREEN after switch.

Char tests updated: Encounter.characterization (2) + Combat.characterization
(2) assert updateDoc on activeDisplay, not setDoc.

BUG-4: prod was already fixed (merge:true), test was RED due to mock
ignoring opts. Now all 3 adapters consistent via updateDoc.

src/tests/HideHpToggle.test.js

@@ -50,14 +50,14 @@ describe('BUG-4: hide-player-HP toggle preserves activeDisplay', () => {
 
     await waitFor(() => {
       const writes = getAdapterCalls().filter(
-        c => c.fn === 'setDoc' && c.path.includes('activeDisplay/status')
+        c => c.fn === 'updateDoc' && c.path.includes('activeDisplay/status')
       );
       expect(writes.length).toBeGreaterThan(0);
       const last = writes[writes.length - 1];
-      // data written must include activeCampaignId AND activeEncounterId
-      // BUG: writes only {hidePlayerHp:true}, clobbering them.
-      expect(last.data.activeCampaignId).toBe('c1');
-      expect(last.data.activeEncounterId).toBe('e1');
+      // patch must NOT clobber activeCampaignId/activeEncounterId.
+      // BUG: setDoc replace writes only {hidePlayerHp:true} → clobbers.
+      // Fix: updateDoc patch — other fields untouched.
+      expect(last.patch.hidePlayerHp).toBe(true);
     }, { timeout: 3000 });
   });
 });