fix(opencode): co-promote the session-URL notice with the feedback on OpenCode 2 (#1515) (#1518)

On OpenCode 2 a plugin message is a pending inbox row; resume: false only
declines the immediate wake. SessionInbox.promote publishes pending steers
as a batch but queued rows one at a time, oldest first, so the queued
notice #1460 introduced was promoted alone by the feedback's own wake and
became its own model turn with the reviewer's annotations behind it.

The notice now rides steer delivery, and feedback that follows an
admitted notice rides steer too, so both enter one promotion and the
agent acts on the annotations. A rejected notice, OpenCode 1, and hosts
without session.synthetic keep the queue delivery unchanged.