DSH: add Cindy-owned activity panels and controlled terminal lifecycle

## 目标

实现有明确 `cindy-dsh` provenance 的计划、任务、终端、job/workflow/schedule activity，不伪称上游未公开的 native UI object。

## 交付

- versioned reducer/panels、stable identity、owner/scope/session checks 与 named IPC actions。
- terminal attach/input/signal/close 与 cancel/disconnect/recovery contracts。

## 验收

- 每个 shipped object 的 action、取消、断线和恢复限制可证明。
- activity 不进入 Orca storage/Worker UI，不持久化 raw runtime JSON。

Blocked by #3776. Blocks #3779.

Canonical plan: `docs/issues/dsh-native-integration/`.

Start by reading the canonical plan in docs/issues/dsh-native-integration/ and the blocking issue #3776. No source files or tests are named, so identify the reducer/panel and IPC entry points there first. Done means the shipped objects have provable action, cancellation, disconnect, and recovery limits without entering Orca storage/Worker UI or persisting raw runtime JSON.

Written by the indexing model from the issue text.