feat(dsh): deliver Cindy-owned DSH control plane

## 背景

DSH 作为 Cindy 的第四个 Agent harness 接入。控制面由 Cindy 自己实现：Desktop Main 拥有 scope、session binding、command receipt、权限、事件投影、恢复与跨端路由；官方 DSH runtime 只是受控执行引擎。

## 架构裁决

- 不等待、不依赖上游另行提供 Native Host API。
- Cindy 只通过公开 ACP v1 控制受管 runtime；不读取私有 JSONL/数据库、不嵌入 Web UI。
- 一个 runtime session 只允许一个 Cindy bridge owner。
- 上游未公开的 UI 对象只能以明确的 `cindy-dsh` provenance 由 Cindy 实现，绝不伪称 native。

## 完成条件

- F0 Cindy Bridge Gate 对固定 release 证明受管 ACP 与 Cindy bridge lifecycle。
- F1–F11 按依赖图交付，现有 Claude Code、Codex、Pi 不退化。
- 未验证能力保持 capability-gated；F11 的真实发布证据和维护者批准前不称完整可用。

## 文档

- Requirements: `docs/issues/dsh-native-integration/dsh-native-integration-requirements.md`
- Technical spec: `docs/issues/dsh-native-integration/dsh-native-integration-technical-spec.md`
- Development plan: `docs/issues/dsh-native-integration/dsh-native-integration-development-plan.md`
- Validation plan: `docs/issues/dsh-native-integration/dsh-native-integration-validation-plan.md`

Blocks: #3771–#3782

Start with the requirements, technical spec, development plan, and validation plan under docs/issues/dsh-native-integration/. Trace the F0–F11 dependency graph and the Cindy bridge lifecycle first. Done requires the documented release evidence, validation of the managed ACP runtime and bridge, preserved Claude Code, Codex, and Pi behavior, and maintainer approval before claiming full availability.

Written by the indexing model from the issue text.