fix: restore packaged runtimes and ship macOS DMG only

Desktop 0.12.7 omitted OpenCode's offline node_modules because the resource
copier excludes node_modules at its source root. Copy from the parent and
verify every prepared configuration file in the final package. Bundle DSH
session projection with the unpacked Host instead of leaving an ASAR-only
external import, and reject external DeepSeek imports in shipped chunks.

Run packaged OpenCode plugin import and the real DSH UtilityProcess handshake
in Windows x64 CI before removing unpacked output. Add regressions using the
actual electron-builder copier and Vite externalization configuration.

Prepare approved Desktop 0.12.8 notes and change macOS defaults and CI to DMG
only. Update aggregation, website downloads and update readers for 12
installers and 20 assets. Current readers retain historical DMG/ZIP support;
the user accepts that older macOS GitHub readers and all older mirror readers
need manual upgrades. Agent remains 0.11.21, with no new Agent or LoongArch tag.

Validation: 3608 tests passed, 0 failed, 61 skipped across 339 files;
typecheck, lint, release-note validation, website static checks and 18 website
tests passed. No local production build or packaged-app launch was performed
at the user's request; actual packaged startup validation runs in CI.

Release note: 修复安装后 OpenCode 离线依赖缺失和 DeepSeek Harness Host 启动退出；macOS 改为仅提供 DMG，受影响旧版用户需从下载页手动升级。

docs/features/deepseek-harness/technical-design.md

@@ -141,6 +141,9 @@ Harness 子进程内控制面不能取代 Main 控制面，Main 控制面也不
 Harness Session 只在当前 Runtime 进程生命周期内存在。释放 GoodBuddy 会话时必须同步释放对应 Harness Agent。
 固定 Host 显式加载 `dsh-session-projection` 的内存 SessionProjectionRegistry，这是
 `0.1.2-rc.1` AgentLoop 的必需依赖；不加载 Session persistence，也不新增磁盘会话副本。
+该依赖与其余 DSH 依赖一起由 Vite 打入 Host，不能从 `app.asar.unpacked` 外部导入
+仅存在于 `app.asar` 的 npm 包。最终打包检查及 Windows CI 的真实 UtilityProcess
+启动探针见 [Runtime 资源与打包](../../../BUILD.md#runtime-资源)。
 
 ## 6. 总体架构