Track requester-controlled task clarification waits #207

Next host-lifecycle prerequisite for #198/#55, following #199. Independent of #201 and #203.

Add explicit requester-controlled input-wait and answer actions using the existing task authorization boundary. A working task may wait on one host-generated question ID; only its requester may answer the current question. Keep one bounded selected question/answer snapshot rather than copying conversation history.

Acceptance:

• Working -> blocked(input) -> working survives restart; blank/oversized input and stale/mismatched question IDs are refused.
• Wrong/anonymous/revoked actors and body actor claims confer no authority.
• Approval waits cannot be replaced or released by answering input. Holds that arrive during an input wait remain tracked, including multiple holds; approving them does not clear the unanswered question.
• Cancellation, failure and stale answers cannot revive terminal tasks.
• No automatic model prompt, new adapter credential, remote execution authority or team-mode gate.

Update host docs, generated patches, the changelog and regression coverage; verify and run mock smoke before handoff for external review.