feat(planning): accept-all-and-check action on the interview page routed to audit-answers

[kyle-sexton]

Problem

/planning:audit-answers exists as a skill, but the interview page has no control that hands a round to it. The V1 design named an optional "Accept all and have agents check them" action.

Evidence

• Issue feat(planning): decide the interview page backlog left after V1 and the redesign #4653, "SPEC section 11 deferred behaviors": the page has no button that hands a round to the skill.
• Skill: plugins/planning/skills/audit-answers.

Proposed approach

Add an "Accept all and have agents check them" page action that posts one event. The interview skill routes that event to /planning:audit-answers. The page gains no validation logic of its own.

Acceptance criteria

• The page shows the action for a round with recommended answers.
• Activating it accepts the round's recommendations and posts exactly one event.
• The skill routes that event to /planning:audit-answers.
• A test covers the event shape and the routing rule.

Context

Refs #4653 (owner decision 2026-09-29, Option B).