Parked-permission retry/rescue logic consolidated into a single object (vt)

The logic that handles a "parked permission" — a tool-approval prompt that survived a session resume or interruption — was previously spread across several separate functions wired manually into the response-handling code. It has now been consolidated into a single object with named methods for firing, handling unexpected responses, arming, checking whether a permission is being held, checking for a pending inherited prompt, and seeding already-handled tool-use IDs.