Feature: Support PreToolUse hook updatedInput for headless question answering

[OneStepAt4time]

Background

Claude Code v2.1.85 added support for PreToolUse hooks to return updatedInput alongside permissionDecision: "allow", enabling headless integrations that collect answers via their own UI.

Feature

When CC asks a question via AskUserQuestion tool, Aegis should be able to intercept it via the PreToolUse hook and provide an answer programmatically.

API

POST /v1/sessions/:id/answer
{
  "questionId": "<tool_use_id>",
  "answer": "<user answer text>"
}

Flow

1. CC invokes AskUserQuestion tool
2. Aegis PreToolUse hook fires with the question
3. Aegis stores the pending question and emits a ask_question status event (already done)
4. External client calls POST /v1/sessions/:id/answer
5. Aegis returns { permissionDecision: "allow", updatedInput: { answer: "..." } } from the hook
6. CC receives the answer and continues

Priority

P1 — This is a key differentiator for headless CC orchestration.

Files

• src/hooks.ts — hook handler for PreToolUse with updatedInput
• src/server.ts — new endpoint POST /v1/sessions/:id/answer
• src/session.ts — pending question tracking
• src/events.ts — question event with ID for correlation

[OneStepAt4time]

Implemented via PR #342. POST /v1/sessions/:id/answer endpoint with configurable timeout. 7 tests for answer flow.