fix(feedback): stamp a native note before the injection reaches the agent

`created_at` was taken on the way back from `_session/steering`, after
the adapter had already handed the text to the agent. The agent can
write its own transcript copy of the message inside that round trip, so
the note could end up NEWER than the copy it caused — and the frontend,
which folds a persisted copy away only when it postdates the note (so
that the same words sent in an earlier round are never hidden), would
then show the message twice.

Taken before the command is enqueued instead, which is also when the
pull path records its own notes. A test pins the ordering against the
instant the connection loop sees the injection.