Remove the steer promotion cutoff: a turn boundary now promotes every
steer pending at promotion time instead of snapshotting the inbox at a
captured sequence, so late-arriving steers ride along into the turn.
Delete legacy projected-prompt synthesis from projectPrompted. The
event-sourced session input migration wiped pre-inbox event history,
so every Prompted event follows an admitted inbox row and a missing or
divergent row on replay is an invariant violation.
Inline the prompt equivalence predicate and update tests that seeded
history with bare Prompted events to publish PromptAdmitted first.
Add SessionTitle service that generates a session title from the
session's sole user message via the customizable "title" agent, then
renames the session. Runs once per session, gated on durable history
having exactly one user message (no default-title string comparison).
Wire it into SessionRunner as a background fork after the first turn's
prompt promotion makes the user message visible; forking before
promotion caused the first-message lookup to see zero rows and silently
no-op.
Closes#34364
