SDK permission handling drops the 'leave questions standing' mode

What

The internal 'leave questions standing' mode, which rejected pending permission and question prompts with "the session is being torn down" when a session shut down, has been removed. This affects sessions driven through the SDK or stream-json, where another program hosts Claude Code and answers its prompts.

• leaveQuestionsStanding, the leftStanding state, the questionsLeftStanding hook and the teardown rejection message are gone. questionsFrozen() no longer depends on it.
• handleElicitation no longer returns cancel because questions were left standing; it cancels only when input is closed or the request was aborted.
• Only the shutdown check now decides whether a control_response is left for the next process, and replies left standing are no longer counted.
• When the host owns standard input, successful can_use_tool answers that were not forwarded are recorded in hostDialogAnsweredRequestIds. Settling a prompt clears that list.
• When no prompt is left pending, the session state flips back from requires-action.

Why

This changes what happens to pending permission prompts when an SDK or remote session is torn down mid-question: they are no longer rejected through a separate teardown mode. Hosts that relied on the teardown message should check how their pending prompts now settle.