match main firebase behavior; fix contract + mismatches

Contract rewritten to match main prod truth:
- require id injection in all doc/collection results
- honor setDoc({merge:true}) (main L1624 + 4 activeDisplay sites)
- drop invented bare<->prefixed cross-lookup tests (main never does this)
- add setDoc{merge}, batch set-only/update-only contract coverage

Fix mismatches vs main:
- subscribeCollection hook now forwards queryConstraints (was dropped;
  LOG_QUERY sort+limit honored again). Mock onSnapshot honors orderBy+limit.
  2 new contract tests prove the chain.
- subscribeDoc/subscribeCollection adapters now forward errCb. App hooks +
  DisplayView propagate subscribe errors to UI (match main onSnapshot 3rd arg).
- ws adapter signatures accept queryConstraints + errCb (interface match).

activeDisplay writes match main:
- 5 unguarded sites -> setDoc({merge:true}) (create-if-missing, not updateDoc)
- 3 guarded sites stay updateDoc

Delete memory adapter: third storage system added complexity, zero value.
firebase-mock covers fast tests, ws covers server path. Factory throws on
unknown mode now.

Delete phantom 'Phase A/B' comment in firebase.js header.

Tests updated to assert setDoc{merge} (not updateDoc) for activeDisplay writes.
83/83 green.

src/tests/Encounter.characterization.test.js

@@ -42,7 +42,7 @@ describe('Encounter -> Firebase', () => {
     expect(call.path).toMatch(/campaigns\/[^/]+\/encounters\//);
   });
 
-  test('togglePlayerDisplay: updateDoc patch on activeDisplay/status', async () => {
+  test('togglePlayerDisplay: setDoc{merge} patch on activeDisplay/status', async () => {
     await setupCampaignAndEncounter('Camp D', 'Enc D');
     await selectEncounterByName('Enc D');
 
@@ -50,33 +50,33 @@ describe('Encounter -> Firebase', () => {
     const eyeBtn = await screen.findByTitle('Activate for Player Display');
     fireEvent.click(eyeBtn);
 
-    await waitFor(() => findCall('updateDoc', 'activeDisplay/status'));
-    const call = findCall('updateDoc', 'activeDisplay/status');
-    // BUG-4 fix: updateDoc patch, not setDoc replace (was clobbering fields)
+    await waitFor(() => findCall('setDoc', 'activeDisplay/status'));
+    const call = findCall('setDoc', 'activeDisplay/status');
+    // main truth: setDoc{merge} patch, not replace (would clobber fields)
     expect(call.data).toMatchObject({
       activeCampaignId: expect.any(String),
       activeEncounterId: expect.any(String),
     });
   });
 
-  test('togglePlayerDisplay off: updateDoc nulls active ids', async () => {
+  test('togglePlayerDisplay off: setDoc{merge} nulls active ids', async () => {
     await setupCampaignAndEncounter('Camp O', 'Enc O');
     await selectEncounterByName('Enc O');
 
     // turn ON
     const onBtn = await screen.findByTitle('Activate for Player Display');
     fireEvent.click(onBtn);
-    await waitFor(() => findCall('updateDoc', 'activeDisplay/status'));
+    await waitFor(() => findCall('setDoc', 'activeDisplay/status'));
 
     // turn OFF
     const offBtn = await screen.findByTitle('Deactivate for Player Display');
     fireEvent.click(offBtn);
     await waitFor(() => {
-      const calls = findCalls('updateDoc', 'activeDisplay/status');
+      const calls = findCalls('setDoc', 'activeDisplay/status');
       const last = calls[calls.length - 1];
       return last.data.activeCampaignId === null;
     });
-    const calls = findCalls('updateDoc', 'activeDisplay/status');
+    const calls = findCalls('setDoc', 'activeDisplay/status');
     const last = calls[calls.length - 1];
     expect(last.data).toMatchObject({ activeCampaignId: null, activeEncounterId: null });
   });