No hook signal distinguishes "turn complete" from "turn ended awaiting a user answer/selection"

Problem

Tools that surface agent state through hooks (working / needs-you / done) can't tell "Claude finished, nothing owed" apart from "Claude ended its turn by asking me a question and is waiting for my answer." Both surface only the Stop hook, so a pending question is indistinguishable from a completed task — you don't get pinged when Claude actually needs you.

Details

• Stop fires when Claude yields for an AskUserQuestion / a multiple-choice or clarifying question — the same event as a completed task, with nothing in the payload marking that user input is required.
• Notification (idle_prompt) does not fire for an AskUserQuestion selection — only for text-input idle. (Reported in #51882, closed for inactivity.)
• The newer PermissionRequest hook covers tool-permission prompts, but not questions/selections.

Request (any one would close the gap)

1. Fire Notification / idle_prompt when awaiting an AskUserQuestion selection (what #51882 asked), or
2. A dedicated "awaiting user input/selection" hook event (the UserInputRequired idea from #10168), or
3. A reason field on the Stop payload distinguishing completed vs awaiting_user_input.

Refs: #51882, #10168, #6454.