message.reaction events are session-scoped (they mutate a chat
transcript), but desktop_ui.emit() was routing ALL events through
HERMES_UI_SESSION_ID — a window/socket identity. The renderer's
gateway-event stream is keyed on the session id, so the frame
landed on a stream that doesn't own the transcript and was never
painted live. The reaction persisted correctly (the DB write is
session-aware), but only appeared after a resume/reload.
Window-level events (pane.reveal, preview.open) continue to route
by HERMES_UI_SESSION_ID unchanged.
Fixes#80678.
dd49b7f69f