Silent desktop updates and the foundation for channel replies

Desktop updates can now download and install silently, with persistent state that survives an app restart. The update controls explain the current setting and recovery path more clearly.

Chat gains the canonical data model needed for channel replies. Inactive threads close instead of lingering forever, removing a specialist from a room updates optimistically, and an exact mention can restore a specialist who was previously removed.

Miniapp permission denials are presented as final decisions instead of offering a retry that cannot succeed. Active execution leases are bounded, repository workspaces publish their complete contents, and voice participant slots stop jumping as the active speaker changes.