feat(cli): bgagent ask Phase 2 (POST /tasks/{id}/asks)

**Context:** ROADMAP.md → `bgagent ask` (Phase 2)

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## Component

Scripts / CLI

## Describe the feature

Mid-run **questions to the agent**: `POST /tasks/{id}/asks`; answers durable as `status_response` events. CLI `bgagent ask ""` with foreground block-and-poll. Enables interactive summaries without burning a separate status API.

## Use case

Operators need "why did you change X?" mid-flight without `nudge`ing implementation guidance. Answers must survive CLI disconnect.

## Proposed solution

1. REST: create ask, poll events by `correlation_id=ask_id`.
2. Agent between-turns hook injects ask as user turn; emits `status_response`.
3. CLI spinner + adaptive poll; `bgagent asks show ` for reconnect.
4. Sync `cli/src/types.ts` with `cdk/.../types.ts`.
5. Fanout Slack renderer for `status_response` (Phase 2).

## Other information

- Full spec: `docs/design/INTERACTIVE_AGENTS.md` §5.5, AD-6/AD-7.
- `status_response` already in fanout allowlist (forward-compat).

- [ ] This might be a breaking change

Lisez d’abord docs/design/INTERACTIVE_AGENTS.md §5.5 et AD-6/AD-7, puis examinez les définitions de types CLI et CDK dans cli/src/types.ts et cdk/.../types.ts. Suivez le flux REST ask, le hook between-turn, l’interrogation des événements, la commande reconnect et la diffusion Slack status_response décrits dans la proposition. C’est terminé lorsque le comportement de la Phase 2 et les types synchronisés couvrent tous les chemins listés.

Rédigé par le modèle d'indexation à partir du texte de l'issue.