Open a locked account whole: calendar, contacts and files too

Switching to a locked account handed to the reader moved only the mail.
Now calendar, contacts and files follow it as well, through a new
viewAccountFor that the three stores use for what they show. Settings,
signatures and push keep ownAccountFor, so nothing of the reader's is
ever written into the locked account (inbuxa AL-7).

web/src/store/session.ts

@@ -19,9 +19,9 @@ interface SessionState {
   /** Selected mail account (defaults to primary). */
   accountId: Id | null;
   /**
-   * A locked account handed to the reader that the mail view shows instead
-   * of their own (inbuxa AL-7). Only mail follows it: settings, filters,
-   * push and everything else stay the reader's own.
+   * A locked account handed to the reader that the app shows instead of
+   * their own (inbuxa AL-7): its mail, calendar, contacts and files. The
+   * reader's settings, filters, signatures and push stay their own.
    */
   viewing: Id | null;
   /** The name of an account whose delegation ended while it was in view. */
@@ -42,6 +42,13 @@ interface SessionState {
   accountFor(cap: string): Id | null;
   /** The user's own account for a capability, whatever they are looking at. */
   ownAccountFor(cap: string): Id | null;
+  /**
+   * inbuxa AL-7: the account calendar, contacts and files show: the locked
+   * account in view, if it offers `cap`, else the reader's own. Never for
+   * anything the reader keeps (settings, signatures, push): those stay
+   * `ownAccountFor`.
+   */
+  viewAccountFor(cap: string): Id | null;
 }
 
 let refreshing: Promise<void> | null = null;
@@ -161,6 +168,13 @@ export const useSession = create<SessionState>((set, get) => ({
   ownAccountFor(cap) {
     return ownAccountForCapability(get().session, cap);
   },
+
+  viewAccountFor(cap) {
+    const { session, viewing } = get();
+    const viewed = viewing ? session?.accounts[viewing] : undefined;
+    if (viewing && viewed && cap in (viewed.accountCapabilities ?? {})) return viewing;
+    return ownAccountForCapability(session, cap);
+  },
 }));
 
 function applySession(s: JmapSession, set: (p: Partial<SessionState>) => void) {