Runtime chat streaming and library prompt controls.

Restored library task selection so clicking a task selects it without opening the full prompt; the prompt modal now opens from the explicit prompt link only.

Streamed MiniBrain runtime conversations and builder-session updates over event-socket channels, with conversation cache merging and polling disabled while sockets are connected.

Added older-message pagination, delegated task/tool progress bubbles, terminal error display, and safer runtime chat cache invalidation.

Updated MiniBrain conversation APIs and React Query hooks for conversation pages, latest-run state, continuation IDs, and clear-session cache resets.