The picker no longer touches the profile default. Model/effort/fast live as
plain UI state persisted in localStorage, so a pick follows across Cmd+N and
restarts instead of snapping back. New chats ship that state through
session.create as per-session overrides; live chats still scope switches to the
current session. Settings -> Model remains the only surface that writes the
profile default.
The gateway now accepts those session.create overrides, builds the agent with
them directly, reflects them in the immediate session.info payload, and writes
the chat's own model_config into the lazy DB row so reconnect/resume restores
that chat instead of the global default.
cb6b4127e7