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/storage/ws.js

@@ -188,7 +188,7 @@ function createWsStorage({ baseUrl, wsUrl } = {}) {
       await api('POST', '/api/batch', null, { ops: normOps });
     },
 
-    subscribeDoc(rawPath, cb) {
+    subscribeDoc(rawPath, cb, errCb) {
       const p = norm(rawPath);
       // Initial value via REST (independent of WS connect).
       storage.getDoc(p).then(cb).catch(() => {});
@@ -201,7 +201,7 @@ function createWsStorage({ baseUrl, wsUrl } = {}) {
       return () => { docSubs.get(p)?.delete(cb); };
     },
 
-    subscribeCollection(rawCollPath, cb) {
+    subscribeCollection(rawCollPath, cb, queryConstraints = [], errCb) {
       const p = norm(rawCollPath);
       // Initial value via REST (independent of WS connect).
       storage.getCollection(p).then(cb).catch(() => {});