mail.google.com
Mark Gmail thread as unread
Input
threadId requiredHex legacy thread id (as returned by search_emails).
account optionalGoogle account email to act as (authuser=). Without it Gmail picks u/0, nondeterministic in a multi-account browser jar.
Output
unread requiredthreadId requiredpage optionalWhich All Mail page the thread was found on (1-based).
already_unread optionaltrue = the thread was already unread; nothing was clicked.
