v0.5.0 — the card stays after the turn ends

The card no longer disappears when the turn ends.

It used to fade out two minutes after the final event. Now it stays where it is — one line above the
composer — and that line is the entry point for "what did it just do?": click to open the rows,
click x to dismiss that one turn. The next turn brings it back on its own.

Past conversations behave the same way: opening one shows the last turn of that conversation,
because the projection keeps exactly one turn of history (the part the card renders). Nothing is
recomputed on the client.

• Removed the two-minute expiry and its timer.
• x dismisses the current turn only; the preference for open/closed is still remembered.
• Host unchanged: this is a Client release, so a page refresh is enough.