The WeChat iLink typing ticket has a 600-second TTL. When a long-running
session exceeds that window, the cached ticket evicts from TypingTicketCache.
Both send_typing and stop_typing silently returned early when the ticket was
None, meaning the TYPING_STOP=2 signal was never sent to iLink. The WeChat
client then showed the typing indicator indefinitely.
Fix: add _ensure_typing_ticket() that transparently refreshes the ticket
via getConfig when the cached one has expired or is missing. Both send_typing
and stop_typing now call this method instead of silently no-oping.
Fixes#38085
