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/firebase.js

@@ -1,10 +1,8 @@
 // firebase.js — storage adapter wrapping Firebase SDK. Default impl (upstream-unchanged).
 // Matches interface of memory.js / ws.js so App.js calls stay identical.
 //
-// NOTE: App.js currently imports SDK directly. This adapter extracted verbatim.
-// Two-phase refactor:
-//   Phase A (now): adapter exists, wraps SDK. Hooks/writes can switch incrementally.
-//   Phase B (later): App.js imports storage factory, drops direct SDK imports.
+// App.js imports SDK via this module (doc, setDoc, etc re-exported) for both
+// the adapter (createFirebaseStorage) and direct SDK calls. ONE import path.
 
 'use strict';
 
@@ -120,21 +118,27 @@ export function createFirebaseStorage() {
     },
 
     // Subscribe = onSnapshot. cb fires immediately + on change. Returns unsubscribe.
-    subscribeDoc(path, cb) {
+    subscribeDoc(path, cb, errCb) {
       recordAdapterCall({ fn: 'subscribeDoc', path });
       return onSnapshot(doc(db, path), (snap) => {
         cb(snap.exists() ? { id: snap.id, ...snap.data() } : null);
-      }, (err) => console.error(`subscribeDoc ${path}:`, err));
+      }, (err) => {
+        console.error(`subscribeDoc ${path}:`, err);
+        if (typeof errCb === 'function') errCb(err);
+      });
     },
 
-    subscribeCollection(collectionPath, cb, queryConstraints = []) {
+    subscribeCollection(collectionPath, cb, queryConstraints = [], errCb) {
       recordAdapterCall({ fn: 'subscribeCollection', path: collectionPath });
       const q = queryConstraints.length > 0
         ? query(collection(db, collectionPath), ...queryConstraints)
         : collection(db, collectionPath);
       return onSnapshot(q, (snap) => {
         cb(snap.docs.map(d => ({ id: d.id, ...d.data() })));
-      }, (err) => console.error(`subscribeCollection ${collectionPath}:`, err));
+      }, (err) => {
+        console.error(`subscribeCollection ${collectionPath}:`, err);
+        if (typeof errCb === 'function') errCb(err);
+      });
     },
 
     dispose() { /* SDK managed; no-op */ },