session.create is intentionally lazy: a brand-new session's state.db row
is only written on the first prompt, so a "New chat" tile opened but
never typed into has a stored id with nothing behind it yet. The
transcript-timeline mount fetch and the periodic active/tile transcript
sync didn't know that and read it anyway, 404ing repeatedly against a
row that cannot exist ("Session not found" x4 in desktop.log before the
first send, #123622).
Track the already-existing "created this run" bookkeeping (used to keep
a flapping-backend resume from being misread as a deleted session) in
its own small module, and skip the transcript/timeline read when a
session created this run still has zero local messages — at that point
there is nothing to fetch, and the empty local view is already correct.
ddd0cc6944