feat(sessions): show a pending-question indicator on session rows

Adds a per-session pending-question badge to sidebar rows, driven by the
live directory-store question state through a dedicated per-session
subscription channel so unrelated streaming never re-renders rows.

Collapsed parent rows roll up pending questions of hidden descendants
from their owning directory stores without bootstrapping them. Question
state is cloned on session delete/archive so badges clear when sessions
disappear. Adds the questionChangeCallbacks sync performance counter,
i18n keys for all locales, and unit tests for the subscription channel
and scope selection.

Fixes #2634

packages/ui/src/sync/child-store.ts

@@ -14,8 +14,10 @@ export type DirectoryStore = State & {
   replace: (next: State) => void
 }
 
-type PermissionSubscriber = () => void
-const permissionSubscribersByStore = new WeakMap<StoreApi<DirectoryStore>, Map<string, Set<PermissionSubscriber>>>()
+type BlockingRequestSubscriber = () => void
+type BlockingRequestSubscribers = WeakMap<StoreApi<DirectoryStore>, Map<string, Set<BlockingRequestSubscriber>>>
+const permissionSubscribersByStore: BlockingRequestSubscribers = new WeakMap()
+const questionSubscribersByStore: BlockingRequestSubscribers = new WeakMap()
 
 type SessionMessageChange = {
   messagesChanged: boolean
@@ -72,12 +74,42 @@ export function markDirectorySessionPartChanged(
 export function subscribeDirectoryPermission(
   store: StoreApi<DirectoryStore>,
   sessionID: string,
-  listener: PermissionSubscriber,
+  listener: BlockingRequestSubscriber,
 ): () => void {
-  let bySession = permissionSubscribersByStore.get(store)
+  return subscribeBlockingRequest(permissionSubscribersByStore, store, sessionID, listener)
+}
+
+export function subscribeDirectoryQuestion(
+  store: StoreApi<DirectoryStore>,
+  sessionID: string,
+  listener: BlockingRequestSubscriber,
+): () => void {
+  return subscribeBlockingRequest(questionSubscribersByStore, store, sessionID, listener)
+}
+
+export function subscribeDirectoryQuestions(
+  store: StoreApi<DirectoryStore>,
+  sessionIDs: readonly string[],
+  listener: BlockingRequestSubscriber,
+): () => void {
+  const unsubscribers = [...new Set(sessionIDs.filter(Boolean))].map((sessionID) => (
+    subscribeBlockingRequest(questionSubscribersByStore, store, sessionID, listener)
+  ))
+  return () => {
+    for (const unsubscribe of unsubscribers) unsubscribe()
+  }
+}
+
+function subscribeBlockingRequest(
+  subscribersByStore: BlockingRequestSubscribers,
+  store: StoreApi<DirectoryStore>,
+  sessionID: string,
+  listener: BlockingRequestSubscriber,
+): () => void {
+  let bySession = subscribersByStore.get(store)
   if (!bySession) {
     bySession = new Map()
-    permissionSubscribersByStore.set(store, bySession)
+    subscribersByStore.set(store, bySession)
   }
   let listeners = bySession.get(sessionID)
   if (!listeners) {
@@ -88,24 +120,28 @@ export function subscribeDirectoryPermission(
   return () => {
     listeners?.delete(listener)
     if (listeners?.size === 0) bySession?.delete(sessionID)
-    if (bySession?.size === 0) permissionSubscribersByStore.delete(store)
+    if (bySession?.size === 0) subscribersByStore.delete(store)
   }
 }
 
-const notifyChangedPermissions = (
+const notifyChangedBlockingRequests = <T,>(
+  subscribersByStore: BlockingRequestSubscribers,
+  counter: "permissionChangeCallbacks" | "questionChangeCallbacks",
   store: StoreApi<DirectoryStore>,
-  current: State["permission"],
-  previous: State["permission"],
+  current: Record<string, T>,
+  previous: Record<string, T>,
 ): void => {
   if (current === previous) return
-  const subscribers = permissionSubscribersByStore.get(store)
+  const subscribers = subscribersByStore.get(store)
   if (!subscribers || subscribers.size === 0) return
+  const changedListeners = new Set<BlockingRequestSubscriber>()
   for (const [sessionID, listeners] of subscribers) {
     if (current[sessionID] === previous[sessionID]) continue
-    for (const listener of listeners) {
-      countSyncPerformance("permissionChangeCallbacks")
-      listener()
-    }
+    for (const listener of listeners) changedListeners.add(listener)
+  }
+  for (const listener of changedListeners) {
+    countSyncPerformance(counter)
+    listener()
   }
 }
 
@@ -239,7 +275,8 @@ function createDirectoryStore(directory: string): StoreApi<DirectoryStore> {
     if (state.projectMeta !== prev.projectMeta) persistProjectMeta(directory, state.projectMeta)
     if (state.icon !== prev.icon) persistIcon(directory, state.icon)
     if (state.session !== prev.session) persistSessions(directory, state.session)
-    notifyChangedPermissions(store, state.permission, prev.permission)
+    notifyChangedBlockingRequests(permissionSubscribersByStore, "permissionChangeCallbacks", store, state.permission, prev.permission)
+    notifyChangedBlockingRequests(questionSubscribersByStore, "questionChangeCallbacks", store, state.question, prev.question)
     notifyChangedSessionMessages(store, state, prev)
   })