feat: add independent managed SSH agent packages

Managed SSH previously tied remote Agent and Runtime artifacts to desktop
packaging and Host activation. Settings now manages verified Linux x64 and
arm64 .gbagent packages explicitly, with source-aligned download and update
plus offline import and export. Each package contains the signed Agent, pinned
Node, and compatible OpenCode Runtime, and project activation never downloads
one automatically.

Dedicated native CI and a protected release workflow publish deterministic,
signed cumulative catalogs to GitHub and Beijing OSS without replacing the
desktop Latest release. Desktop packaging is metadata-only, remains independent
of Agent artifacts and signing credentials, and Linux desktop releases add RPM
installers.

The managed SSH path also keeps model credentials in Main, enforces Ask as
read-only, verifies signed Agent and Runtime inputs, preserves ACP recovery, and
reports Host update cancellation and failures accurately.

Release note: 远程项目现可在“设置”中手动下载、更新或离线导入签名 Agent 包，桌面安装包与远程组件发布相互独立；Linux 桌面版同时新增 RPM 安装包。

docs/README.md

@@ -39,6 +39,7 @@ GoodBuddy 文档按“文档类型 → 功能域”组织。新增文档应先
 - [长期助手路线图](./roadmap/long-term-assistant-roadmap.md)
 - [电脑控制实施状态](./status/computer-control-implementation-status.md)
 - [知识检索评估](./quality/knowledge-retrieval-evaluation.md)
+- [GoodBuddy 龙芯（LoongArch）预览版构建与功能列表](./development/loongarch-preview-build.md)
 - [统一界面设计系统](../UI-DESIGN.md)
 
 ## 目录规则
@@ -47,6 +48,7 @@ GoodBuddy 文档按“文档类型 → 功能域”组织。新增文档应先
 2. 跨功能技术总纲放在 `docs/architecture/`。
 3. 产品级设计放在 `docs/design/`，路线图和实施状态分别放在 `roadmap`、`status`。
 4. 测试方法、评估协议和质量报告放在 `docs/quality/`。
-5. 一个概念只能有一份权威定义；其他文档链接到它，不复制另一套术语。
-6. Task、Job、Run、Subagent 和 Conversation 的含义以
+5. 开发环境、实验性构建和移植说明放在 `docs/development/`。
+6. 一个概念只能有一份权威定义；其他文档链接到它，不复制另一套术语。
+7. Task、Job、Run、Subagent 和 Conversation 的含义以
    [Task 与 Job 统一领域模型](./prd/task-and-job/task-and-job-model.md) 为准。