Miguel Palhas
ad2e700391
Pressing Spawn while reading a session split that pane in half. It now opens the draft in its own tab, leaving the current tab untouched. Scoped to the explicit Spawn affordances (the header button and the sidebar empty state, both via OPEN_SPAWN_EVENT). "Spawn similar" and the fast-forward key deliberately keep splitting: both act on the session in front of you, so a pane beside it is the point. Reusing an empty pane (#72) is unchanged — that path never split anything. Closes #100