[httpsphl]

Part 4 of the ideas from 2026-10-04.

• A message from one bot to another is a call until the other picks it up (readAt). A pill shows both mascots stacked in round badges with "Calling Writer •••"; once picked up it reads "Writer picked it up" with a check for 4 s, then leaves. A dead delivery ends it; a call nobody picks up in an hour stops being one.
• Shown over the caller's composer (floating, nothing in the chat moves) and in the crew page's header, for every bot of the crew. One pill per pair of bots, the latest call.
• The store keeps who called whom from message.created (new store/calls.ts); whether it was picked up comes from the delivery, which every connection reloads, so a reconnect never leaves a call ringing.
• The pill's mascots glance at each other like everywhere else; screen readers hear the caller first.
• The dev preview has Writer call Revisão three times.
• Spec 15.3 updated.

Test plan

• pnpm check (new calls.test.tsx: what is a call, ring/pick-up/dead/expiry, one per pair, chat and crew page)
• Preview: the pill over Writer's composer and in the Research header, ringing and picked up
• Real Claude: ask a bot to send a task to another and watch the pill until the other one starts