Public Access
Each live session gets its credit window reset — the unacknowledged bytes died with the old page, and their acknowledgement is never coming — and its SessionOpened frame again, flagged as a replay so the page can tell a reattach from a genuinely new session. A session whose shell already ended gets nothing: its scrollback lived only in the page that is gone, and a frame implying otherwise would lie. RendererReattached is the seam for what the workspace has no business owning: the font size and the selected tab live in the shell, which re-pushes them from its own subscription.